FcγRIIIa genotype, but not FcγRIIa genotype, is associated with acquisition of HIV infection after vaccination with rgp120. Cumulative HIV incidence curves for (A) FcγRIIIa genotype (P = .035) and (B) FcγRIIa genotype are determined by Cox proportional hazard models that are weighted to account for case-cohort design and under sampling of subgroups of uninfected subjects. The curves are unadjusted for race, behavioral risk score, and location.