Abstract Marihuana and hashish are the most widely used illicit drugs. They are derived from the hemp plant, Cannabis sativa . Among the diverse chemicals in the plant, more than 20 so-called cannabinoids have been isolated and their chemical structures elucidated (1). In 1965, Mechoulam and coworkers (2,3) isolated △ 9- tetrahydrocannabinol (△ 9-THC) from cannabis extract and demonstrated that it was responsible for the psychopharmacologic effects of cannabis in animals. Later, Isbell (4) and Hollister et al. (5) confirmed these findings in man. This paper reviews the physiologic disposition of △ 9-THC in man; the disposition of △ 9-THC in animals has been reviewed elsewhere (6, 7, 8).