Research on loneliness and research on social support offer complementary perspectives on how social relationships affect health and well being. However, despite considerable overlap, loneliness and lack of social support reflect deficits of different kinds of social exchanges and these deficits have distinct consequences for well being. Social support research emphasizes the importance of various kinds of help provided by others in ameliorating the effects of stressful events, while loneliness research emphasizes the importance of opportunities for pleasurable companionship and intimacy in enhancing psychological well being. Help provided by others is most useful in reducing threats to well being, while companionship is most useful in providing positive inputs to well being. Individuals who are lonely and those who lack social support are likely to differ not only in the kinds of concrete interpersonal experiences they lack but also in how they interpret their situation. The public meaning of loneliness also differs from that of low social support. Cultural stereotypes portray lonely people as failures in the social marketplace, while people who do not seek help are often seen as heroic or highly competent. These conceptual differences, however, do not necessarily reflect empirical differences. Research suggests that measures of loneliness and measures of social support are strongly correlated. In order to identify the extent to which loneliness and lack of social support represent distinct conditions, theoretically guided analyses of the actual interpersonal experiences that evoke feelings of loneliness and feelings of being unsupported should be conducted. (BL)