Chemical Abstracts Service
A chemical-information service that produces scientific literature, substance, structure, and reaction databases.
Last updated August 25, 2026
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Overview
Chemical Abstracts Service (CAS) is a division of the American Chemical Society that develops and maintains information resources for chemistry and related scientific fields. Based in Columbus, Ohio, CAS grew out of Chemical Abstracts, an abstracting and indexing publication that began in 1907. Its work has expanded from printed summaries of chemical literature into a large digital information infrastructure used by researchers, universities, corporations, publishers, libraries, patent professionals, regulators, and other technical organizations. CAS indexes research articles, patents, conference proceedings, technical reports, dissertations, books, and other scientific material. The coverage described for Chemical Abstracts has included approximately 8,000 journals and other publication types in at least 50 languages, together with patent specifications from multiple countries and international organizations. The resulting bibliographic and abstracting content is organized principally through the CAplus database, while substance identities and related structure information are maintained in the CAS Registry system. The CAS Registry is one of the service's most recognizable contributions. It assigns individual chemical substances a CAS Registry Number, together with an index name and a representation of the substance's structure. These identifiers are widely used to distinguish substances whose names may vary across languages, suppliers, regulatory systems, and nomenclature conventions. The Registry has also incorporated sequence information from CAS and GenBank. The reference material describes the Registry as containing information on more than 200 million organic and inorganic substances and approximately 70 million protein and nucleic-acid sequences as of 2023. CAS distributes its information through several products and platforms. SciFinder provides access to chemical, bibliographic, substance, structure, and reaction information through a graphical interface. Its web successor, SciFinder-n, was introduced in 2017 with an updated interface and search capabilities. STN International, operated jointly by CAS and FIZ Karlsruhe, is aimed principally at professional information specialists and uses a command-language interface while providing access to CAS and other databases. CASSI, the CAS Source Index, is a free online reference tool for identifying journal titles, abbreviations, CODENs, ISSNs, publishers, publication histories, and language information. The organization has repeatedly adapted its delivery model to changes in scientific publishing and information technology. Chemical Abstracts moved from volunteer-supported abstracting toward a more formalized operation, with volunteer abstractors phased out by 1994. Print publication of Chemical Abstracts ended on January 1, 2010, reflecting the migration of the service to electronic databases and search platforms. In 2021, CAS introduced a rebrand and revised mission language emphasizing responsiveness to changing scientific communities and industries. In 2022, it made almost half a million CAS Registry Numbers available under an open license through the Common Chemistry project. CAS is not a separately traded public company. It operates within the American Chemical Society, a nonprofit scientific organization. Its role is best understood as a specialized professional information and publishing service rather than as a conventional consumer brand. Its distinctiveness rests on the scale and normalization of its chemical data, the continuity of its literature coverage, and the integration of textual, bibliographic, substance, structure, reaction, and sequence information.
History
Chemical Abstracts Service developed from the growth of chemical abstracting and indexing in the United States during the early twentieth century. Its immediate predecessor was the Review of American Chemical Research, an abstracting publication begun by Arthur A. Noyes in 1895. In 1907, William A. Noyes expanded that effort and helped establish Chemical Abstracts as a separate publication devoted to collecting and organizing chemical research. Noyes became the first editor of the new publication. Chemical Abstracts remained associated with the American Chemical Society in various forms from 1907 onward. For many years its offices were located on or near the campus of Ohio State University in Columbus, including facilities associated with McPherson Laboratory and Watts Hall. E. J. Crane, who had become editor in 1915, played a central role in the publication's development. When Chemical Abstracts Service became a division of the American Chemical Society in 1956, Crane became its first director. Dale B. Baker succeeded him in 1958 and oversaw a period characterized by expansion, modernization, and international cooperation with other information organizations. CAS was an early adopter of computing for the storage, organization, and distribution of scientific information. A major development came in 1965 with the introduction of the CAS Chemical Registry System. The system assigned unique CAS Registry Numbers to chemical substances and connected those identifiers to standardized index names and chemical-structure representations. The identifiers later became important to government agencies, fire departments, industrial organizations, and other users that needed an unambiguous way to identify substances despite differences in naming practices. The organization's physical infrastructure also expanded during this period. In 1965, CAS moved from its earlier Columbus locations to a large site on the west bank of the Olentangy River north of the Ohio State campus. An expansion designed to accommodate the processing of hundreds of thousands of new research reports opened in May 1973. The Columbus campus became a recognizable part of the local scientific and cultural landscape. During the second half of the twentieth century, CAS broadened its coverage beyond a conventional printed index. It developed databases containing bibliographic records, abstracts, substance information, chemical structures, reactions, and patent material. The two principal databases supporting many CAS products became CAplus, which provides references and abstracts, and the CAS Registry, which provides substance and structure information. CAS also participated with FIZ Karlsruhe in operating STN International, a professional search service that uses a command-language interface and provides access to multiple scientific databases. Electronic delivery gradually replaced print distribution. SciFinder brought CAS content to chemists through a graphical search interface capable of keyword, structure, and reaction searching. A web version became available in 2008, and SciFinder-n was introduced in 2017 as a web-only platform with an updated user experience and search functions. SciFinder Scholar, a related academic product, was discontinued in 2023. Print publication of Chemical Abstracts ended on January 1, 2010. CAS also maintained reference tools for the serial-literature environment. CASSI, the CAS Source Index, moved from print and CD-ROM formats to a free online service in 2009. It allows users to verify journal titles, abbreviations, CODENs, ISSNs, publishers, publication histories, and language information for scientific and technical publications dating from 1907 onward. The American Chemical Society designated CAS an ACS National Historic Chemical Landmark in 2007, recognizing its importance as a comprehensive repository of chemical and related scientific research. In 2021, CAS updated its visual identity and mission language to emphasize responsiveness to changing scientific industries and communities. In 2022, it expanded public access to part of its identifier infrastructure by making almost half a million CAS Registry Numbers available under an open license through Common Chemistry. As of 2023, the CAS Registry was described as covering more than 200 million organic and inorganic substances and about 70 million protein and nucleic-acid sequences. CAS remains an active ACS division and a major global provider of curated chemical information.
- 2022
Common Chemistry opens access to selected Registry Numbers
[1]CAS announced open-licensed access to almost half a million CAS Registry Numbers through Common Chemistry.
- 2021
CAS undertakes a brand refresh
[1]CAS updated its logo, brand identity, and mission language.
- 2017
SciFinder-n launches
[1]CAS introduced SciFinder-n as a web-only platform with updated search and interface capabilities.
- 2010
Chemical Abstracts print publication ends
[1]CAS discontinued the print edition and continued delivering its information through electronic products.
- 2009
CASSI becomes an online reference service
[1]The formerly print and CD-ROM journal-reference compilation became available as a free online search tool.
- 2008
SciFinder web version becomes available
[1]CAS expanded SciFinder from a client application to a web-accessible platform with graphical searching.
- 2007
CAS receives ACS National Historic Chemical Landmark designation
[1]The American Chemical Society recognized CAS for its significance as a comprehensive repository of chemical research.
- 1965
CAS Chemical Registry System is introduced
[1]CAS introduced its system for assigning unique Registry Numbers and associated substance records.
- 1956
CAS becomes an ACS division
[1]Chemical Abstracts Service became a division of the American Chemical Society, with E. J. Crane as its first director.
- 1907
Chemical Abstracts is established
[1]William A. Noyes expanded the earlier abstracting effort and became the first editor of Chemical Abstracts.
Products and positioning
A specialized, authoritative information infrastructure for chemistry and related sciences, combining large-scale literature indexing with standardized substance, structure, reaction, and sequence data.
Bibliographic database
CAplus
CAplus is a principal CAS database for chemical and related scientific literature. It brings together bibliographic records and abstracts from journal articles, patents, conference proceedings, technical reports, dissertations, books, and other publications. Its coverage supports literature discovery across chemistry and neighboring disciplines and forms a core data layer for CAS search products.
Substance and structure database · 1965
CAS Registry
The CAS Registry organizes chemical substances and related biological sequence information. Each indexed substance can receive a CAS Registry Number, an index name, and a graphic representation of its chemical structure. The system is designed to resolve ambiguity caused by synonyms and differing nomenclature practices and is used across research, industry, and regulatory contexts.
Chemical information search platform
SciFinder
SciFinder provides graphical access to CAS chemical and bibliographic information. Users can search literature and substances by keywords, chemical structures, and reactions, making it useful for research planning, prior-art investigation, and synthesis discovery. A web version was introduced in 2008. SciFinder Scholar, an academically oriented variant, was discontinued in 2023.
Web chemical information platform · 2017
SciFinder-n
SciFinder-n is CAS's web-only chemical information platform, introduced in 2017. It provides access to CAS literature, substance, reaction, and structure content through a redesigned interface and expanded search functions. The product is intended for researchers and organizations that need integrated discovery across chemical publications and substance data.
Professional scientific information network
STN International
STN International is a scientific and technical information network operated jointly by CAS and FIZ Karlsruhe. It is aimed primarily at professional information specialists rather than casual users and uses a command-language interface. In addition to CAS databases, STN provides access to other scientific and technical information resources.
Serial-publication reference tool · 2009
CASSI
CASSI, or the CAS Source Index, is an online reference service for identifying and verifying scientific and technical publications. It provides journal titles and abbreviations, CODENs, ISSNs, publishers, publication histories, and language information. Its coverage extends from 1907 to the present and includes serial and non-serial publications.
Open chemical reference resource · 2022
Common Chemistry
Common Chemistry is a CAS project that makes selected chemical identity information more openly accessible. In 2022, CAS announced that almost half a million CAS Registry Numbers would be released under an open license through the project, expanding public access to a portion of its identifier infrastructure.
Marketing campaigns
- 2021CAS brand refresh
Global
CAS introduced a new logo and refreshed brand identity while presenting a mission more explicitly focused on responding to changes in scientific industries and communities.
Outcome. The organization continued operating under the CAS name with a more contemporary positioning for its scientific information services.
Brand decisions
2022
Open selected CAS Registry Numbers through Common ChemistryStrategyBackground
CAS maintained a large proprietary substance-identification infrastructure while also developing ways to make selected chemical identity data more accessible.
Action taken
CAS announced the open-licensed release of almost half a million CAS Registry Numbers through Common Chemistry.
Aftermath
The initiative expanded public access to a selected portion of CAS identifier data without indicating that the entire CAS Registry had become open.
2017
Launch SciFinder-nProduct launchBackground
CAS sought to provide its chemical and bibliographic content through a modern web-based search experience.
Action taken
CAS released SciFinder-n as a web-only product with an updated interface and improved search functions.
Aftermath
SciFinder-n became the newer generation of CAS's flagship researcher-facing search platform.
2010
End print publication of Chemical AbstractsStrategyBackground
CAS had developed electronic databases and online delivery systems that increasingly replaced printed abstracting and indexing workflows.
Action taken
The organization stopped publishing the print edition of Chemical Abstracts on January 1, 2010.
Aftermath
CAS continued distributing its literature and chemical information through digital products and database platforms.
Recent events
- 2022
CAS releases CAS Registry Numbers through Common Chemistry[1]
Product launch
CAS announced that almost half a million CAS Registry Numbers would be available under an open license through the Common Chemistry project.
- 2021
CAS refreshes its brand and mission[1]
Campaign
CAS adopted a new brand identity and revised mission language focused on responding dynamically to changes in science, technology, and scientific communities.
- 2017
CAS introduces SciFinder-n[1]
Product launch · Product generation
The American Chemical Society introduced SciFinder-n as a web-only successor platform with an updated interface and enhanced search functions while retaining CAS chemical and bibliographic content.
- 2010
CAS ends print publication of Chemical Abstracts[1]
Other · Product generation
Chemical Abstracts ceased print publication as CAS concentrated its information services in electronic databases and online delivery.
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