INTRODUCTION This study@ conducted for the American Petroleum Institute of Washington@ D.C@ was designed to assess the toxic effects of API 83-19 when administered by inhalation. Sprague-Dawley (COBS CD[SD]BR) rats were exposed to vapors of this petroleum derived hydrocarbon for a single four-hour period on 26 June@ 1986. On day 14 post-exposure@ surviving animals were sacrificed for gross postmortem examination and preservation of selected tissues. The study was conducted by Hazleton Laboratories America@ Inc.@ 1330-B Piccard Drive@ Rockville@ Maryland 20850@ and was conducted in compliance with the Good Laboratory Practice Regulations of the Environmental Protection Agency (40 CFR@ Part 160).