Friendly social relations during free time, referred to here as leisure-based sociability, constitute a prominent reward of participation in groups based on voluntary membership, consisting for this review mainly of amateurs, hobbyists, volunteers, and their associations. This benefit is analyzed according to two subtypes: sociable nonprofit associations and social clubs. The goal of this issue of the Voluntaristics Review is to examine the leisure component of these two subtypes as framed in the serious leisure perspective (SLP), put nonprofit sociability in organizational context, and then...