The biotransformation of (+)-, (-)-, and (+-)-alpha-pinenes, (-)-beta-pinene (nopinene), (-)-cis-pinane, (+)-3-carene, (-)-cis-carane, myrcene, and p-cymene in rabbits was investigated. The major metabolites were as follows: (-)-trans-verbenol from (+)-, (-)-, and (+/-)-alpha-pinenes; (-)-10-pinanol and (-)-1-p-menthene-7,8-diol from (-)-beta-pinene; (-)-alpha-terpineol and (-)-trans-sobrerol from (-)-cis-pinane; (-)-m-mentha-4,6-dien-8-ol, 3-caren-9-ol, (-)-3-carene-9-carboxylic acid, and 3-carene-9,10-dicarboxylic acid from (+)-3-carene; carane-9,10-dicarboxylic acid from (-)-cis-carane; and myrcene-3(10)-glycol, myrcene-1,2-glycol, uroterpenol, and p-cymene-9-carboxylic acid from p-cymene. These metabolisms include allylic oxidation, epoxidation, stereoselective gem-dimethyl hydroxylation and its oxidation, cleavage of a conjugated double bond by epoxidation, and regioselective oxidation, some of which are not found usually in chemical reactions, and due to which various new compounds were determined. This biotransformation of the monoterpene hydrocarbons gave some insect pheromones in high yield.U