The purpose of this article is to present some characteristics of the Swedish voluntary sector. With the help of recent research results, the voluntary sector and its wide range of activities is placed into a comprehensive structure that includes historical and cultural roots as well as the connection between the sector and the emergence of the Swedish welfare state. What is characteristic for the Swedish welfare model also explains, in important respects, the conditions of the voluntary sector and the way in which it finds articulation. However, this is not in itself a sufficient explanation if we are to understand the many-sided phenomenon represented by the Swedish voluntary sector. The role played by the tradition of popular mass movements in shaping the voluntary sector of today must also be taken into account. After a general overview in the first half of the article, two aspects of Swedish voluntary sector activities are presented to illustrate these points: the high level of volunteerism of the population and the particular character and role of voluntary organizations in the field of social care.