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. The tapes consist of two files: Inventory Preferred Name File and Inventory Synonym Name File. The first file contains the CAS Registry Number, preferred CA Index Name, molecular formula, and other appropriate information for each non-confidential Inventory chemical substance. The entries are in ascending CAS Registry Number order. The second file is a file of synonymous chemical names for the same substances listed in the Preferred Name File. Its entries are ordered alphabetically by name with each name accompanied by the same information for the substance as appears in the Preferred Name File.