The purpose of this meta-analysis is to examine the effects of adventure programs on a diverse array of outcomes such as self-concept, locus of control, and leadership. The meta-analysis was based on 1,728 effect sizes drawn from 151 unique samples from 96 studies, and the average effect size at the end of the programs was .34. In a remarkable contrast to most educational research, these short-term or immediate gains were followed by substantial additional gains between the end of the program and follow-up assessments (ES = .17). The effect sizes varied substantially according the particular program and outcome and improved as the length of the program and the ages of participants increased. Too little is known, however, about why adventure programs work most effectively.