This article summarizes evidence from meta-analyses of outdoor education, psychotherapy, and education which can he used to help determine the relative efficacy of adventure therapy programs. The major outdoor education meta-analysis by Hattie, Marsh, Neill, and Richards (1997) cites an effect size of.34 for immediate program effectiveness. Meta-analytic studies of innovative education programs in school settings report similar effects (Hattie et al., Hattie, 1992, 1993), while psychological training meta-analyses report slightly higher effects (Lipsey & Wilson, 1993), and meta-analyses of psychotherapy effectiveness find stronger effects (Casey St Berman, 1985; Smith, Glass, & Miller, 1980). This article derives outcome benchmarks for adventure therapy program outcomes taken from existing outdoor education, psychological, and educational meta-analyses, and recommends that the benchmarks be used in adventure therapy research and evaluation to allow for more accurate assessments of program's effectiveness. The suggested benchmarks should be used only as guides, and should be refined in future by meta-analyses of adventure therapy outcomes.