After-school programs have gained considerable attention for their potential to reduce delinquency after school. The current study assessed the factors related to effective after-school programming utilizing survey data from a recent evaluation of after-school programs. Program participation was responsible for reducing property, violent, and general offending, but not substance use. Further analysis concluded that the hypothesized increase in parental supervision, increase in positive peer influence, and reduction in unsupervised time were insufficient to explain the ability of after-school programs to elicit behavioral improvements. After-school programs were also found to be equally effective for youth from high and low income families.