OBJECTIVE: To assess the effect of a change in human immunodeficiency virus (HIV) testing policy on HIV testing rates in an urban maternity clinic population. METHODS: Since 1995, our institution has provided pretest counseling and voluntary HIV testing to all pregnant women. After the 1999 Institute of Medicine recommendation of HIV testing with patient notification as a routine component of prenatal care, we conducted a prospective study to determine whether this policy would increase our HIV screening rates. The intervention incorporated HIV testing into the routine battery of tests drawn at antenatal care. Not to be tested required active refusal. The intervention group was comprised of all women receiving an initial antenatal visit in one of our eight maternity clinics between August 1, 1999, and July 30, 2000. The control group was comprised of all women presenting for prenatal care in the same clinics during the year before the intervention. RESULTS: The 3415 women in the intervention group and 3778 controls were similar with respect to most demographic and risk factors. After the intervention, HIV testing increased from 75% to 88% (P < .001). Among all women in both years of the study, women who were in the intervention group, less than 20 years of age, or who had a history of substance abuse, were more likely not to refuse testing. CONCLUSION: After implementation of a policy of routine HIV testing with active patient refusal, HIV testing rates increased among pregnant women in our large, urban obstetric clinic population. © 2001 by the American College of Obstetricians and Gynecologists.