Data collected during an evaluation of a multi-site trial of an enhanced after-school program were used to relate quality of program implementation to student experiences after school. The enhanced after-school program incorporated a drug use and violence prevention component that was shown to be effective in previous research. Building on Durlak and Dupre's (Am J Community Psychol 41:327-350, 2008) dimensions of implementation, we assessed the level of dosage, quality of management and climate, participant responsiveness, and staffing quality achieved at the five program sites. We evaluated how these characteristics co-varied with self-reported positive experiences after-school. The study illustrates how multiple dimensions of program implementation can be measured, and shows that some but not all dimensions of implementation are related to the quality of student after-school experiences. Measures of quality of management and climate, participant responsiveness, and staffing stability were most clearly associated with youth experiences. The importance of measuring multiple dimensions of program implementation in intervention research is discussed. © 2010 Society for Community Research and Action.