This paper tests the hypothesis that the psychological vulnerability of disadvantaged persons to undesirable life events can be explained by the joint occurrence of high event exposure and low social support resources in such persons' lives. Data from a panel study of 1,106 individuals in Chicago are utilized to examine this hypothesis. Social support is operationalized as the relative presence or absence of an intimate, confiding relationship. Analyses show that differential vulnerability cannot be accounted for by the joint occurrence of undesirable events and lack of support. A significant negative main effect of social support on psychological distress is revealed, suggesting that support counterbalances, rather than interacts with (buffers), the impacts of life stress. Explanations for these findings are offered.