Nineteen metabolites of heptyl-delta-1-THC have been identified in mouse liver using combined g.l.c. and mass spectrometry following i.p. administration of the drug. All metabolites contained either hydroxyl or carboxylic acid functions, the positions hydroxylated (2'', 3'', 6 and 7) were the same as those found previously for delta-1-THC in this species. The relative abundance of acid metabolites was much lower than for the corresponding metabolites produced from delta-1-THC itself, but hydroxylation was more extensive with metabolites containing up to four hydroxyl groups being observed.