Group researchers have long been interested in how group members respond to deviance, defined as the violation of prescriptive norms about how members should think, feel, or act. Valuable perspectives on reaction to deviance have been offered by scholars in several disciplines, including social psychology, evolutionary psychology, and sociology. Most of the theoretical and empirical work on reaction to deviance assumes that this behavior has negative consequences for group welfare and hence elicits efforts designed to reduce or eliminate it, including the threat or use of punishment. However, there is increasing interest in the other side of the coin, namely cases in which deviance has positive consequences for group welfare and hence is tolerated or even celebrated. In addition, researchers are also devoting increased attention to the causes of deviance, that is, the reasons why some group members choose to violate prescriptive norms even though doing so may elicit punishment. The papers in this Special Issue, which investigate deviance in a wide range of situations, illustrate cutting-edge work on each of these themes.