Although evolutionary and social-structural models predict that women will be more supportive than men in relationships, behavioral studies fail to confirm this difference. We predicted instead that gender differences in support will be moderated by stress, and that men will provide lower-quality support primarily when their stress is high. We predicted further that the detrimental effects of stress on men's support will be more evident when men are responding to women's emotionally toned expressions of stress than when men are responding to women's affectively neutral expressions of stress. Stressed and unstressed men and women were observed providing support to a stressed relationship partner. While unstressed, men and women generally provided similar support to the stressed partner. While stressed, men provided lower-quality support than did comparably stressed women, but only in response to emotionally toned expressions of stress. Thus, gender differences in support may arise because women are better able than men to regulate other people's emotional distress while managing stresses of their own.