SummaryThe lowest effective dose of bezitramide, a new analgesic, was evaluated in 15 patients with severe chronic pain due to cancer or (pre) gangrene; 5-10 mg of bezitramide daily provided fair to good pain relief in these patients. Bezitramide had an onset of action of 1-1 1/2 hour and a duration of action of 8-14 hours. It also had potent antitussive properties. Severe side-effects did not occur. In a double-blind, cross-over trial, including 8 patients with severe chronic pain, a good correlation was obtained between the logarithm of the daily dose of bezitramide and that of dextro-moramide.The potency of bezitramide appeared to be related to the severity of the pain. The study also suggests that«analgesic equivalence of drugs»does not exist unless the kind and degree of pain is properly determined.The respiratory depressant action of 5 mg of bezitramide was evaluated in 10 patients. No significant changes were observed in any of the parameters studied, with the exception of the respiratory rate, which may be considered the least reliable factor for the assessment of the respiratory dpressant effect of analgesics.