Although immunocompromise due to HIV-1 (HIV) infection increases the importance of receipt of routine childhood vaccines, such vaccines appear to have decreased immunogenicity in these children. The study's objectives were to evaluate the immunogenicity of Haemophilus influenzae type B(Hib) conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load. The concentration of antibody to polyribosylribitolphosphate (PRP) was measured at approximately nine and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study. Of 227 children at the 9-month visit known to have received age-appropriate immunization with a Hib conjugate vaccine, the geometric mean antibody concentration (GMAC) was lower among 35 HIV-infected children (1.64 μg/ml) as compared to uninfected children (2.70 μg/ml), although the difference was not statistically significant. The proportion of children with antibody concentrations ≥ 1.0μg/ml did not differ significantly according to HIV infection status (73% uninfected, 74% infected). Neither the GMAC nor the proportion of children with antibody concentrations ≥ 1.0 μg/ml varied significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage, or viral load(p ≥ 0.37). Similar results were obtained among 127 children (17 HIV-infected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time did not differ significantly among HIV-infected as compared to uninfected children (p = 0.87). These results suggest that HIV-infected children with mild-moderate disease progression may have an adequate quantitative antibody response to Hib conjugate vaccines during the first two years of life. Additional investigations of the immune response to Hib conjugate vaccines, including the qualitative antibody response to immunization, should be pursued.