Chronic stress-induced behavioral disturbances have been used as experimental models of depression. One of them is the deficit of fighting behavior induced by 16-day application of various unpredictable stressors. In the present study we investigated the effect of beta-adrenoceptor antagonists (propranolol, pindolol, nadolol and acebutolol) on electric footshock-induced fighting behavior in chronically stressed (14 various stressors over 16 days) male Wistar rats. It was found that the number of fighting attacks was reduced by about 50-80% in the rats submitted to chronic stress. Prolonged, 14-day, but not acute, treatment with propranolol, pindolol or nadolol (but not acebutolol) counteracted the deficit of aggression induced by chronic stress. It is suggested that beta-adrenoceptor antagonists which penetrate the blood-brain barrier may prevent the behavioral changes induced by chronic stress.