Public health agencies have recommended that the criteria for the use of highly active antiretroviral therapy should not be modified because of pregnancy. However, little information has been published with regard to the degree to which these recommendations are being followed. We report here the frequency of highly active antiretroviral therapy use among pregnant women in the Women's Interagency HIV Study and compare the frequencies of its use by pregnant women meeting published criteria for implementing highly active antiretroviral therapy and its use by nonpregnant women meeting the same criteria.From October 1994 through November 1995, a total of 2059 human immunodeficiency virus type 1-seropositive women were enrolled in a cohort study. Participants were evaluated at baseline and at 6-month intervals with standardized interview instruments. In addition to a general physical examination at each visit, patients had a urine pregnancy test performed and were asked about current pregnancies, pregnancies since the last visit, and which antiretroviral medications they had used since the last visit. Highly active antiretroviral therapy was defined according to 1997 National Institutes of Health guidelines.At each calendar interval after October 1996, a greater proportion of nonpregnant women than pregnant women reported the use of highly active antiretroviral therapy. The use of monotherapy declined for both groups during the course of multiple calendar periods (P <.01), although the use of monotherapy remained higher among the pregnant women. In any given calendar period, pregnant women meeting published criteria for highly active antiretroviral therapy use were slightly less likely than similar nonpregnant women to receive highly active antiretroviral therapy (odds ratio, 0.28-0.98). Because of the sample size these differences reached significance in only one calendar period (P =.02). With time pregnant women did demonstrate an increase in the percentage receiving highly active antiretroviral therapy. In nearly all calendar periods a larger percentage of pregnant than nonpregnant women were receiving a regimen that included zidovudine.Highly active antiretroviral therapy is being received by an increasing percentage of women who meet published criteria for its use, and pregnancy is a relatively small impediment to its use. Further efforts are needed to bolster the use of highly active antiretroviral therapy by all appropriate candidates and to ensure equal access to this therapy for pregnant women. Because of the increasingly frequent use of highly active antiretroviral therapy during pregnancy, ongoing efforts are needed to monitor any long-term effects of in utero exposure to multiple antiretroviral agents.