Gender differences in social support tend to suggest that women have larger social networks and both give and receive more support than men. Nevertheless, although social support has been identified as protective of mental health, women have higher rates of psychological distress than men. We examine the prospective association between social support and psychological distress by gender in a cohort study of middle aged British Civil Servants, the Whitehall II study. In this sample we found that women have a larger number of close persons than men although men have larger social networks. We also found that the effects of marital status, social support within and outside the workplace and social networks on subsequent occurrence of psychological distress were similar for men and women independently of baseline mental health status.