Butorphanol (l-N-cyclobutylmethyl-3,14-dihydroxy morphinan), a potent analgetic agent of the narcotic antagonist type with a low abuse potential in laboratory animals, was evaluated for antitussive activity in unanesthetized guinea-pigs and dogs. S.c. it was over 100 times more active than codeine, dextromethorphan and dl-pentazocine and about 20 times more active than morphine in the guinea-pig, while in the dog it was 100, 10 and 4 times more active than codeine, dl-pentazocine and morphine, respectively. Orally, butorphanol was 15-20 times more active than either codeine or dextromethorphan in both species. Naloxone reversed the antitussive effects of butorphanol, codeine, morphine and dl-pentazocine, while those of dextromethorphan were not antagonized. The antitussive effect of butorphanol and morphine lasted about 4 h, and both compounds were longer acting than codeine. Butorphanol was equally effective against cough of pathological origin and against experimentally induced cough in the dog.