Negative intergroup processes such as prejudice and conflict have been a traditional focus of social psychological research, while work that explicitly focuses on the determinants of positive intergroup processes is still in its infancy. Reflecting these relatively recent developments in the social and behavioral sciences, this volume's contributions represent current directions in psychological theorizing and research on positive and proactive behavior across group boundaries. One intriguing feature of positive cross-group behaviors is that they can be conceived, at one and the same time, as individual, interpersonal, and collective phenomena. Accordingly, this volume is organized into three sections that represent these different levels of analysis. This multilevel approach represents a distinctive perspective that extends contemporary work on positive intergroup behavior. At a more general level, then, one important future outcome of this work could be a more nuanced picture of human social behavior in the context of groups.