THE need for a potent nonaddicting analgesic has always been great. Nalorphine, a narcotic antagonist, was found to have distinct analgesic activity,1 but because it had undesirable psychotomimetic effects,2 it was introduced clinically as a narcotic antagonist. Pentazocine, a weak narcotic antagonist derived from the benzomorphan nucleus, has been claimed not to produce tolerance and physical dependence.3 This is a report of the effects of pentazocine administered for prolonged periods in two patients with chronic pain of nonmalignant origin.Case ReportsCase 1. J.M., a 59-year-old former meperidine addict, had frequent documented severe anginal pains for years. From February, 1967, . . .