Social researchers have independently investigated behaviors in voluntary association membership and participation in outdoor recreation activities. A small amount of scholarly work has theorized a link between activity in voluntary associations and recreation behavior. These studies have concentrated on the associational affiliations of outdoor recreationists, and their concern for the environment. The purpose of this study was to determine if differences exist between outdoor recreationists who are members of environmental/outdoor recreation voluntary associations, and those who are nonmembers. Organizational membership was designated as the dependent variable. Independent variables were designed to assess (1) incentives for voluntary association membership, (2) motivations for participation in outdoor recreation activities, (3) environmental concern, and (4) social class. A random sample of outdoor recreationists was drawn from the California membership of a large recreational equipment cooperative (R.E.I. Co-op). Data were collected by mail survey. Of the 1500 questionnaires sent, thirty-four were undeliverable, and 1085 were returned for a response rate of 74.0 percent. The sample reflected a substantially higher organizational membership level than the general population with a forty percent membership rate. Members were differentiated from nonmembers by significantly higher ratings on (1) instrumental incentives (public goods) for membership in voluntary associations, (2) intellectual motivations for participation in outdoor recreation, (3) environmental concern, and (4) age and education level. A discriminant function analysis identified instrumental incentives as the most powerful predictor of organizational membership. Results indicated public goods are a primary incentive for outdoor recreationists to join voluntary associations. This suggests a need to re-define instrumental benefits in light of the personal values associated with them. A common thread of intellectual pursuit distinguished members from nonmembers. Intellectual motivations for outdoor recreation, education level, age and environmental concern provided evidence that members are somewhat more oriented toward intellectual development, suggesting that environmental and outdoor recreation-related voluntary associations might benefit from focusing on the educational benefits of membership, and directing promotional communications through channels used by outdoor recreationists. Given the findings of a strong relationship between outdoor recreation and voluntary association membership, further scholarly work should concentrate on the instrumental and intellectual benefits of both behaviors to promote understanding of their synergy.