This article uses longitudinal data from the British Household Panel Study to examine trends in the level of membership in a range of voluntary associations from 1991 to 2007. It has been suggested that the membership of voluntary associations is in decline in western societies and the analysis examines the trajectory of the number of memberships with age for four 10-year age cohorts born between 1935 and 1975. The results for men show lower levels of membership over time for the 1955–1964 and 1965–1974 cohorts in comparison to those of earlier born cohorts. For women, levels of membership were only notably lower for the 1965–1974 cohort. The differences in the probability of belonging to an organisation between cohorts were similar in magnitude to those between categories of social class and education. Cohort differences in the membership of voluntary associations are interpreted to reflect primarily the impact of changing social and economic conditions on individual’s capacity for involvement.