INTRODUCTION Commercial hexane was given to male and female rats by nose-only inhalation exposure for six hours on a single occasion in order to assess its potential acute effects on operant behavior. The study was initiated (date protocol signed by Study Director) on February 16@ 1989@ and was performed at Bio-Research Laboratories Ltd. between August 9@ 1989 (day of treatment for first replicate) and September 1@ 1989 (last day of operant behavior testing). All raw data@ the protocol and the final report have been retained in the scientific archives of this laboratory. This study was conducted in accordance with the EPA Good Laboratory Practice Regulations (TSCA 40 CFR Part 792) and test guideline 798.6500 with modifications as per the commercial hexane Test Rule 40 CFR 799.2155. The rat was the species required in the Test Rule and the Sprague-Dawley strain was selected as it is an accepted strain for use in toxicity evaluations. The test article was administered by inhalation since this is a possible route of human exposure under conditions of use and was requested in the Test Rule. The high dose (target - 9@000 ppm) was selected in order to allow a safety factor between it and the lower explosive limit (12@000 ppm). The low and intermediate doses were selected based on the dose-range requirements in the Schedule Controlled Operant Behavior guideline (Federal Register 798.6500).