To understand the effects of after-school programs, people need to understand the effects of various "dosages." The Harvard Family Research Project, an agency that devotes considerable resources to the study of after-school programs, recommends three categories for measuring dosage: (1) "intensity"; (2) "duration"; and (3) "breadth." Intensity is the amount of time youth attend a program during a given period. Duration is the history of attendance, often expressed as the number of total years in an after-school program. Breadth of attendance refers to the variety of activities that youth attend within and across programs. Measuring breadth of activities, together with intensity and duration, seems a worthwhile approach to future after-school evaluations.