The Chemical Information System (CIS) is a system of approximately 30 databanks available as a dial‐up online source of interactively available information for chemical compounds and their properties. The system was formerly known as the NIH/EPA Chemical Information System on account of its inception and development by two US Government agencies — The National Institutes of Health and Environmental Protection Agency. It is in particular the involvement by the EPA that explains the emphasis of the system on environmental information and the importance of the CIS as a source of data in this area. The databanks are by and large numeric and text databanks containing actual values and observations (quantitative and qualitative results), in contrast to bibliographic databases which, in general, contain only references to the sources of information. The data is compiled by many different producers and ranges widely in terms of applications. The information available can be broadly categorised as: