In a double-blind, 5-way crossover designed study, single doses of placebo, 2 doses of codeine sulfate (60 and 120 mg), and 2 doses of benzopyranoperidine (2 and 4 mg) were administered orally to 35 patients who required analgesics for chronic pain due to malignancies. Benzopyranopyridine is an analogue of delta-9-tetrahydrocannabinol and was chosen on the basis of its sedative, hypnotic, and analgesic properties in animals. Pain relief scores indicated a degree of relief of clinical significance with 120 mg of codeine but no consistent difference between placebo and any other active agent. On the basis of the data, bezopyranoperidine (2 or 4 mg) is not as effective as codeine (120 mg or 60 mg) and not more effective than placebo in relieving pain due to cancer; indeed, pain perception appeared to be augmented by both doses.