Presented is research exploring the relationships between outdoor leisure participation and pro-environmental attitudes and behavior. The seven hypotheses investigated related to determinants of leisure behavior, attitudinal consequences of this behavior, and the relationships among group membership, attitudes, and pro-environmental behavior. These hypotheses were tested using data from two samples of students from a large state university: (1) members of a class in social problems, and (2) members of the hiking division of an outdoor recreation club. Likert scales were employed to measure two attitudinal and two behavioral variables. Correlational analyses showed that membership in a scouting organization and parental education level are significant predictors of leisure behavior. In addition, appreciative leisure behavior was associated with nature appreciation, and nature appreciation was associated with environmental concern. Membership in the recreation club correlated with both nature appreciation and environmental concern. Regression analysis revealed that of nine independent variables, only environmental concern and appreciative leisure participation were significant predictors of pro-environmental behavior. (Author/WB)