The computer-readable TSCA Chemical Substance Inventory is issued periodically to provide chemical substance information for those substances on the non-confidential substance identity portion of the TSCA Master Inventory File. For a complete understanding of the data contained on these tapes, it is necessary to consult the introductory material of the printed 1985 Edition and the 1990 Supplement to 1985 Edition. These tapes contain no TSCA Confidential Business Information. They have been prepared by Chemical Abstracts Service, a Division of the American Chemical Society, under contract to the U.S. Environmental Protection Agency. There are two major differences between these tapes of Inventory chemical substance information and the printed editions of the Inventory: the tapes do not include the EPA Accession Numbers or generic names for confidential substance identities; and synonyms in the Synonym File are those names provided on Inventory reporting forms, however the printed Inventory editions contain additional synonyms from the Chemical Abstracts Service data base.