Morphine metabolism was studied in 12 normal subjects. Six were studied before and while receiving propranolol, 20 mg every 6 hr, and 6 were studied before and while receiving propranolol, 40 mg every 6 hr. The study was performed to determine whether propranolol affects morphine metabolism or morphine‐induced respiratory depression. Plasma and urinary levels of free morphine and conjugated morphine when propranolol and morphine were given together were similar to the levels after morphine alone. Respiratory minute volumes, while breathing a 4% CO2 in air mixture, were also unchanged from control. The findings indicate that propranolol does not affect morphine metabolism or morphine‐induced respiratory depression in man.