Of the 11 individuals with both A*68:02 and B*42-C*17, five acquired HIV-1 at rates similar to those in carriers of B*42-C*17 alone; these 11 were treated as part of the B*42-C*17 group. Differences in acquisition-free time among the three HLA subgroups were tested for significance by the log-rank and Wilcoxon methods. Estimates of relative hazards (RH) of HIV-1 acquisition are based on Cox proportional hazards models. The numbers of subjects remaining at-risk at successive follow-up intervals are tabulated below the Kaplan-Meier plots. The seroconversion rate does not reflect the overall rate in the entire ZEHRP cohort, because couples in this study were selected for clinical and behavioral HIV-1 risk characteristics.