Individual male and female Sprague-Dawley rats with indwelling jugular catheters were subjected to restraint stress both without and with pretreatment with 1 g/kg ethanol (i.p., 20% w/v in water). Plasma norepinephrine (NE) and epinephrine (E) were determined prior to restraint and at 5, 15 and 30 min after the onset of immobilization. Overall, ethanol increased the baseline levels of both catecholamine slightly and transiently but markedly decreased the stress response of both NE and E. The extent of the stress response alone and its reduction by ethanol varied markedly among animals and between the sexes. Female rats showed more varied and higher stress responses and a slightly different response to ethanol. Individual baseline values of NE or E without or after ethanol did not predict the intensity or duration of the stress response or its reduction by ethanol. The total stress response over the entire stress period without ethanol was mostly determined by the 5-min stress response, whereas the total stress response with ethanol was mostly determined by the 15- and 30-min stress responses. The stress response without ethanol predicted strongly its reduction by ethanol; the greater the stress response without ethanol the greater its reduction by ethanol. Our data obtained in rats support the 'tension reduction hypothesis' of human alcoholism and would place individuals with a high stress response at greatest risk to abuse alcohol.