PURPOSE: Although several studies have identified a positive association between recreational facility availability and physical activity, few have examined facility attributes beyond availability and involved minority adolescents. This study examines how both objective and perceived measures of the facility environment are associated with urban adolescents' use of parks and physical activity. METHODS: Study participants included 329 adolescents from two high schools in Baltimore, Maryland, the majority (69%) of whom was African American. A Web-based survey assessed park use, neighborhood crime, and park availability, quality, and use by friends and family. Geographical Information Systems data were used to develop objective measures of park availability and crime. Physical activity data were obtained from 316 participants using accelerometers. Hypotheses regarding environmental correlates of park use and physical activity were tested using logistic regression models (for park use) and linear regression models (for physical activity). RESULTS: Perceptions of greater park availability, quality, and use by friends were associated with a significantly greater likelihood of an adolescents' park use. Perceptions of more park availability was associated with higher levels of physical activity, although this association was marginally significant. Objective measures of park availability and objective and subjective measures of crime were not associated with either park use or physical activity. CONCLUSIONS: Efforts to promote park use for physical activity among urban youth should increase awareness of park availability, improve perceptions of park quality, and utilize social networks.