Studies at Lovelace Inhalation Toxicology Research Institute (ITRI) under the technical proposal 'Studies on the Absorption of Inhaled Hydrocarbon Vapors' were designed to determine if there are significant differences in the dose received for hydrocarbon vapors having different chemical structures. These studies are nearing completion. Results show that significant differences in dose, on a per kilogram body weight basis, occur for different hydrocarbons inhaled at the same vapor concentrations. This is the sixth quarterly report for the project. It covers the period from November 13, 1986 through February 12, 1987. The sixth quarter activities included author revision and in-house review of a manuscript titled 'Uptake of 19 gasoline-related hydrocarbons by F344 rats,' drafting the final report for the first year efforts; and initiating exposures of rats to 14C-radiolabeled octane. In addition, Mr. Rodney C. Anderson of API carried out a quality assurance site visit on February 18, 1987.