Two psychological defense mechanisms, repression and self aggression, were studied in 23 young female migraine patients who had not been receiving treatment for their complaints and in 23 relatively headache free matched controls. All subjects were psychology students. Each subject was classified as high or low on repression and self aggression using the defense mechanism inventory. During three separate sessions: adaptation, intelligence test and real-life stress (an examination which was part of the psychology curriculum) pulse amplitudes of the temporal and digital arteries, frontal, temporal and corrugator EMGs, forehead temperature, skin conductance, and heart and respiration rate were measured. The migraine patients showed a trend towards more repression of their emotions and significantly more self aggression than the controls. Self aggression appeared to be positively associated with the headache frequency in the migraine group. With regard to the physiological measurements, in both groups repressors showed a modest tendency to enhanced sympathetic activity. Self aggression was not found to be related to any physiological measure of sympathetic activity, but, instead, related to less temporal blood flow. In general, associations were found between psychological defense mechanisms and physiological activity, which is suggestive of the existence of physiological pathways along which emotional inhibition might contribute to an attack of migraine after a stressful situation.