BACKGROUND: Little attention has been given to exposure to crime as a possible socioenvironmental contributor to variability in urban childhood asthma prevalence. OBJECTIVE: To determine the association of violent crime, property crime, and drug abuse violations with childhood asthma prevalence in Chicago. METHODS: In 2003-2005, the Chicago Initiative to Raise Asthma Health Equity conducted an asthma screening survey of children in grades K to 8 attending Chicago public and Catholic schools. Crime data were obtained from the Chicago Police Department. In addition to simple regression analysis, multilevel logistic regression analysis was performed to estimate the effect of criminal activity on neighborhood asthma variance. RESULTS: Of the surveys returned, 45,371 (93%) were geocoded into 247 neighborhoods. Neighborhoods were divided into quartile groups by mean asthma prevalence (9%, 12%, 17%, and 22%). Criminal activity (annual incidence per 100,000 people) was significantly higher (P < .001) in neighborhoods with a high asthma prevalence, especially drug abuse violations, which increased more than 6-fold (461 vs 2,921), and violent crimes, which increased more than 3-fold (448 vs 1,566). After adjusting for community race/ethnicity, only violent crime continued to be significantly associated with the neighborhood asthma prevalence (odds ratio, 1.27; 95% confidence interval, 1.04-1.55, P < .05). When considered alongside sociodemographic and individual characteristics, violence continued to contribute significantly (P < .05), explaining 15% of neighborhood variation in childhood asthma. CONCLUSIONS: Evidence suggests an association between violent crime and childhood asthma prevalence in Chicago. A deeper understanding of the mechanisms that underlie this association may lend insight into potential interventions to address urban asthma.