This study utilized a historical cohort to examine the relationship between maternal cocaine use during pregnancy and the occurrence of congenital cardiovascular abnormalities. All neonatal drug screens performed at Boston City Hospital during an 18-month period were reviewed (n = 554); for 214 (39%) screened high-risk neonates, results of toxicologic screens were positive for cocaine, and 340 (61%) neonates had no detectable cocaine. We compared the occurrence of cardiovascular malformations and electrocardiographic abnormalities in these two groups. Matches were sought between these 554 infants and our pediatric cardiology data base, which consisted of inpatient consultation, outpatient consultation, and electrocardiography. Forty-nine patients had drug screens and were also entered into our cardiology data base: 25 had both consultations and electrocardiograms, and 24 had electrocardiograms only. The rate of cardiac anomalies among the cocaine-positive infants was significantly higher (relative risk = 3.7; 95% confidence interval: (1.4, 9.4)) than the rate of these anomalies among the cocaine-negative comparison group (65/100 vs 18/1000); the rate for cocaine-positive infants was also significantly higher than published rates for general populations of infants. Several electrocardiographic abnormalities, high-grade ventricular ectopy, and cardiorespiratory arrests were also noted in our study population. We conclude that cocaine exposure during prenatal life appears to predispose infants to structural cardiovascular malformations, electrocardiographic abnormalities, and, possibly, cardiopulmonary autonomic dysfunction.