Over the past two decades, state and federal restrictions of public smoking have become increasingly common. The resulting controversy has generally focused on the research evidence regarding the physiological effects of second-hand smoke while ignoring relevant psychological aspects of smoker-nonsmoker conflict. In this article I review the literature on the psychological consequences of smoker-nonsmoker interaction, interpreting these results from the framework of social psychological research on inter-group conflict. From this review I conclude that: a) smoker-nonsmoker conflict shares many characteristics of other ingroup-outgroup interactions; b) both groups are served by the legislated separation of these groups; and c) such separation can be successfully accomplished only when close attention is paid to subtle environmental cues. Finally, theoretical benefits of studying smoker-nonsmoker conflict from a social psychological perspective are discussed.