Particular HLA alleles are associated with reduced human immunodeficiency virus replication. It has been difficult, however, to characterize the immune correlates of viral control. An analysis of the influence of major histocompatibility complex class I alleles on viral control in 181 simian immunodeficiency virus SIVmac239-infected rhesus macaques revealed that Mamu-B^*17 was associated with a 26-fold reduction in plasma virus concentrations (P < 0.001). Mamu-B^*17 was also enriched 1,000-fold in a group of animals that controlled viral replication. Even after accounting for this group, Mamu-B^*17 was associated with an eightfold reduction in plasma virus concentrations (P < 0.001). Mamu-B^*17-positive macaques could, therefore, facilitate our understanding of the correlates of viral control.