Background. Gender differences in coronary heart disease are mirrored by gender differences both in cardiovascular reactivity to stress and in the nature and content of social support networks. However, little research has examined the association between cardiovascular reactivity in the laboratory and social support outside; and none has established whether gender differences in such associations can elucidate relevant psychosomatic mechanisms. In addition, in general, studies of cardiovascular reactivity fail to take adequate account of cardiovascular response habituation. Purpose: The present study sought to examine gender differences in associations between psychometrically assessed social support and cardiovascular reactivity and, in particular, response habituation patterns. Method. Ninety-two undergraduate men and women underwent two consecutive cardiovascular reactivity assessments, after having provided psychometric assessments of quantity and quality of social support in ordinary life. Results: Inverse associations between social support and cardiovascular reactivity during the second assessment suggested that highly-supported women exhibited cardiovascular response habituation. For men, the opposite trend-that of support-related cardiovascular sensitization-was found. Results were unaffected by performance of the task used to elicit reactivity or by participant ratings of task dimensions. Conclusions: These findings suggest that men and women differ in the degree to which social support in ordinary life moderates cardiovascular stress responses in laboratories. This difference is highlighted when looking at how cardiovascular responses fluctuate over repeated testing. Habituation-sensitization patterns suggest that, when dealing with difficult tasks, women may derive benefit from background social relationships whereas men may find that such background relationships bring additional pressures.