This article reports the results of a meta-analysis using 50 experimental studies (256 effect sizes) of the overjustification effect. In general, we found support for the effect across age, dependent measure, and design type in specific situations where it is predicted to occur. Findings are less supportive of the theory for situations where there should be no difference between experimental and control groups (e.g. non-contingent or unexpected reward). Suggestions for future research are made.