The effects of single oral doses of nabilone, a synthetic cannabinoid, were studied in eight anxious volunteer subjects. Each subject had two exposures to placebo and three dose levels of nabilone at one-week intervals in a single-blind balanced Latin-square design after the nabilone dose range was determined by each subject's response to a test dose. Heart rate and blood pressure were monitored. The Profile of Mood States (POMS), a self-rating adjective checklist, was used as the quantitative measure of subjective effects. Four subjects performed a continuous avoidance procedure. High doses (4 or 5 mg) of nabilone produced orthostatic hypotension in these subjects. Mild dose-related increases in heart rate also occurred. Despite the occurrence of highly significant levels of sedation, there were no significant effects of nabilone on the continuous avoidance procedure. Two of these four subjects experienced an antianxiety effect from low (1 or 2 mg) nabilone doses. Four other subjects received comparatively lower doses of nabilone and performed on three behavioral tasks at intervals before and after drug: a recognition memory procedure, a task requiring spaced responding at a controlled rate, and a reaction time task. In these subjects there were no reliable effects on blood pressure or heart rate, no significant subjective effects on the POMS, and no antianxiety effects. Drug effects were also minimal on the three behavioral tasks.