Ethological and radioimmunological techniques were used to examine the effects of psychotropic agents on the behaviour of the male Papio hamadryas and the hormonal activity of the steroid-producing glands at physiological rest and during emotional stress. Prior (15 minutes before immobilization) intramuscular administration of haloperidol, 0.1 mg/kg, amitriptyline, 2.0 mg/kg or diazepam, 0.76 mg/kg, was demonstrated to produce no stress protective effect, but to result in predominant effects of these drugs in the poststress period, or even in enhanced stress-induced behavioral and hormonal changes.