The research and theoretical contributions of international and multidisciplinary scholars have advanced our understanding of the role of play in evolution and behavior. The diverse articles in this volume range from theoretical and conceptual advances, scientific investigations, to discourse about applied issues and different dimensions of play. The authors provide excursions into the adaptive, cultural, and social significance of play. The databased papers fall into four categories: the role of age, gender, and ethnicity in play participation, social-cognitive connections to play, fighting and play fighting, and play and process in adulthood.Play is defined as behavior that is not necessary to survival and yet is undertaken voluntarily as a method by which to improve the quality of life. This study, addressing the definition, role, and characteristics of play, falls within the research of education, psychology, anthropology, sociology, leisure studies, and primatology. The play of humans and nonhumans takes a variety of forms and serves multiple purposes within mental and emotional states of being. The motivation and impact of play behavior varies with the type of play performed. The studies included in this volume address simple games, more complex creative activities, the emotional implications of play throughout adult life, and the role of play in human social construction.