Dronabinol, delta-9-tetrahydrocannabinol in sesame oil, has been used for several years as an antiemetic for patients receiving cancer chemotherapy. In combination studies with prochlorperazine, enhancement of efficacy, as measured by duration of episodes of nausea and vomiting and by severity of nausea, has been found. The incidence of psychotropic effects from dronabinol appears to be decreased by concomitant administration of prochlorperazine. In open pilot studies, dronabinol caused weight gain in seven of ten patients with symptomatic HIV infection. In both HIV and cancer patients, dronabinol improved appetite at a dose which was well tolerated for chronic administration.