The integrative model for child development and ecodevelopmental theory suggest that macro factors, such as socioeconomic status, ethnicity, culture, and immigration influence the settings in which adolescents engage. The goal of this investigation was to use a combination of deductive and inductive qualitative analysis to describe the mechanisms by which these macro factors might be related to Mexican-origin adolescents' participation in organized after-school activities. Qualitative data were collected through focus group interviews with 44 adolescents, 50 parents, and 18 activity leaders from 2 neighborhoods that varied in ethnic composition and average family income. Results indicated that family socioeconomic status might be related to adolescents' participation through financial resources and parents' work. Ethnicity was identified as a predictor of participation via experiences with ethnic discrimination, particularly in the neighborhood with a low percentage of Hispanic families. Cultural values and practices were related to participants' preferences for particular activities (e.g., bilingual, church-sponsored) and adolescents' participation in activities. Immigration seemed to be a factor in parents' familiarity with and beliefs about organized activities. (Contains 1 figure, 3 tables, and 1 footnote.)