Mice were exposed to the smoke from placebo marihuana cigarettes treated with phencyclidine hydrochloride (PCP . HCl). A dose-related decrement in motor performance was observed after exposure to the smoke from cigarettes containing 10-15 mg of PCP . HCl. Tissue levels of 3H-PCP, 3H-PC (pyrolysis product), and 3H-metabolites were measured in several tissues up to 7 days after exposure to 50 mg of 3H-PCP . HCl. 3H-PCP levels were highest in liver followed by lung, brain, fat, and plasma for the first 10 min after exposure. The 3H-PCP concentration in all tissues, except fat, declined during the subsequent 50 min. Liver and lung contained the highest levels of 3H-metabolites during this hour, followed by plasma, fat, and brain. Brain levels of 3H-PCP correlated well with the magnitude and duration of behavioral effects observed (r = 0.98). 3H-PC was also well absorbed from smoke as evidenced by initial tissue levels comparable to those of 3H-PCP, but they declined more rapidly than 3H-PCP levels. Excellent correlations were obtained between 3H-PCP and 3H-PC concentrations in plasma and those in liver, lung, and brain. 3H-PCP was not detected in any tissue 3 days after smoke exposure. At 1 and 3 days, radioactivity corresponding to metabolites persisted in liver and lung, but had largely disappeared by 7 days.