THIS IS a report of observations made on 1,109 surgical patients to whom was administered Nu-22061 (3-hydroxy-N-methylmorphinan hydrobromide) or morphine sulfate during the postoperative period. The primary purpose of the project was to compare the duration of action of the two drugs and the complications resulting from their administration. Secondarily sought was information on the relative intensities and duration of pain following various operations and the efficacy of a certain drug in treating pain at a specific site. Denton and Beecher2 have focused attention on the difficulties inherent in the clinical evaluation of analgesic drugs. At the same time. such testing is recognized as a necessary complement to experimentation on animals and normal human volunteers, because the response to medication of patients suffering pain is often different. This experiment failed to compare satisfactorily the duration of action of the two drugs under study. It is believed that the