The role of hormonal contraceptive use in the effectiveness of highly active antiretroviral therapy (HAART) was examined among participants in the Women's Interagency HIV Study who were followed from HAART initiation to 2001. Propensity score selection was used to match 77 hormonal contraceptive users with 77 nonusers on age, race, and pre-HAART CD4-positive T-lymphocyte (CD4+ cell) count and viral load. The authors compared hormonal contraceptive users and nonusers with regard to the CD4+ cell count and viral load responses to HAART upon initiation. Proportional hazards analyses were used to assess the effect of hormonal contraceptive use on times to increases in CD4+ cell count of 50 cells/mm(3) and 100 cells/mm(3) and achievement of an undetectable viral load. There were no statistically significant differences in CD4+ cell counts and log viral load responses by hormone use after HAART initiation, except in log viral load at the third visit after initiation (p = 0.047). Time-dependent hormonal contraceptive use was not a statistically significant predictor of achieving increases in CD4+ cell count of 50 cells/mm(3) and 100 cells/mm(3) or an undetectable viral load (p = 0.517, p = 0.751, and p = 0.218, respectively) after HAART initiation. In conclusion, the authors did not find substantial evidence that use of hormonal contraceptives strongly affected responses to HAART.