Chemical Abstracts Service

The CAS (Chemical Abstracts Service) Registry is the largest database of chemical substance information in the world containing more than 23 million organic and inorganic substances and 41 million sequences. The CAS REGISTRY mostly covers substances identified from the scientific literature from 1957 to the present. Approximately 4,000 new substances are added each day.

Each substance in REGISTRY is identified by a unique numeric identifier called a CAS Registry Number. A CAS Registry Number includes up to 9 digits which are separated into 3 groups by hyphens. The first part of the number, starting from the left, has up to 6 digits; the second part has 2 digits. The final part consists of a single check digit.

CAS is located in Columbus, Ohio.