INTRODUCTION The objective of this study was to determine the toxicity of a selected petroleum-derived hydrocarbon@ API 83-18@ when administrated to rabbits over a 4-week period by dermal application. Dosing was initiated on September 24@ 1984 and was completed on October 23@ 1984. All animals were terminated by October 26@ 1984. This study was run concurrently with two companion studies assessing two additional API compounds. These studies are reported separately as TLI projects 1711(1) and 1711(2). Each of the companion studies had its own control group and three treated groups. A pilot five-day dermal study in rabbits (Phase I) was performed in order to determine the dose levels to be used during this study (Phase II). Phase I dosing was initiated in June 11@ 1984 and was completed in June 15@ 1984. Terminal sacrifice occurred in June 22@ 1984. The report of the Phase I study is presented in Addendum I of this report.