This document announces the 1998 reporting period for the Toxic Substances Control Act (TSCA) Inventory Update Rule (IUR) and contains technical amendments to the rule to update the reporting instructions. The IUR requires manufacturers and importers of certain chemical substances included on the TSCA Chemical Substance Inventory to report current data on the production volume, plant site, and site- limited status of the substances. The 1998 reporting period is from August 25, 1998 to December 23, 1998.