Community service often involves sustained prosocial actions by individuals. This article focuses on one kind of such actions, volunteerism. Volunteerism involves long–term, planned, prosocial behaviors that benefit strangers, and usually occur in an organizational setting. A selective review of the literature on the correlates of volunteerism is presented. One part of the review concerns the relationship between dispositional variables and volunteerism; it includes new data from an on–line survey that show significant relationships among personality traits, religiosity, and volunteer activities. The other part concerns how organizational variables, alone and in combination with dispositional variables, are related to volunteerism. A theoretical model of the causes of sustained volunteerism is presented and the practical implications of this model are discussed.