Objective: To determine whether the occurrence of new-onset bronchospasm or the recrudescence of asthma is associated with the use of cocaine. Methods: A consecutive sample of patients presenting to an inner-city adult ED with new-onset bronchospasm or recrudescence of bronchospasm after >5 years were prospectively enrolled in a case-control prevalence study. The bronchospasm patients were queried as to their exposure to illicit drugs, and urine was obtained to screen for cocaine and its metabolite, benzoylecgonine. An age- and sex-matched control group was composed of randomly chosen subjects without respiratory complaints or a history of asthma. The control group was also screened by urine toxicology for cocaine and its metabolite, benzoylecgonine. Results: In the asthma group, 21/59 (36%) had a urine toxicologic screen positive for cocaine metabolite (benzoylecgonine). Of the 21 with a positive screen for cocaine, 8 denied illicit drug abuse. Among the 13 patients reporting drug use, 10 said that they smoked crack and 3 snorted cocaine. In the control group, 8/53 (15%) were positive. Multivariate logistic regression analysis, with adjustment for age and sex, indicated that the use of cocaine was associated with a 3-fold higher prevalence of new-onset bronchospasm or recrudescence of asthma (OR = 3.28, 95% CI: 1.26 to 8.50). Conclusions: There appears to be an association between cocaine use and new-onset bronchospasm or recrudescence of asthma in this inner-city ED population. Further study is necessary to determine the basis for this association.