The author examines the social organization of the modern leisure experience of amateurs, hobbyists, and career volunteers, showing how activities are organized on a routine basis to facilitate their pursuit, and what happens to impact them. He discusses the concept of social world, the serious leisure perspective, and the qualities of serious pursuit; members of leisure social worlds and the activities they pursue, such as cogitative, artistic, and collecting pursuits and volunteering; their culture and communications; and the issue of the differences separating the casual and serious leisure social worlds.