OBJECTIVE To determine the rate of substance use among Utah's pregnant women, who are primarily white and middle class, for comparison to rates reported in studies of inner-city populations. METHODS Urine specimens and demographic data were obtained anonymously from women who delivered infants at ten hospitals in urban and suburban Utah. Urine samples were screened by enzyme immunoassay for amphetamines, marijuana, cocaine, methadone, opiates, benzodiazepines, and ethanol. RESULTS Among 792 women screened, the mean age was 26.2 years, 86.1% were white, 62.9% were multigravidas, and 66.3% had private insurance. Cocaine was detected in nine samples (1.1%), illicit amphetamines in five (0.6%), marijuana in 23 (2.9%), ethanol in 32 (4.0%), over-the-counter amphetamines in 51 (6.4%), and benzodiazepines in seven (0.9%). The prevalence rate for women positive for illicit drugs and alcohol combined was 7.8%. Cocaine-positive and marijuana-positive women were more likely to be non-white or Hispanic and to have Medicaid or no insurance than were women negative for either substance. Women with Medicaid or no insurance were four times more likely to be positive for illicit substances (10.7%) than were those with private insurance (2.3%) (P = .0001). CONCLUSIONS The rates and patterns of substance use differ between Utah's pregnant women and inner-city populations. The patterns in Utah may be more representative of many communities in the United States that have a predominantly middle-class, white population.