Nausea and vomiting are frequent and distressing side effects of cancer chemotherapy and the severity of these symptoms contributes to the decreased ability of patients to undergo long-term chemotherapy. The phenothiazines have marginal value for nausea and vomiting and more effective antiemetic therapy is needed. THC has recently been identified to contain significant antiemetic potential. This randomized, double-blind, placebo controlled study compares the antiemetic effectiveness of 9THC with a standard phenothiazine antiemetic, prochlorperazine. Furthermore, since THC can induce tolerance to THC this study also examines whether 9THC alters drug handling of the chemotherapeutic agents.