Blood samples from patients with plasma HIV-1 RNA <20 copies/ml for more than 2 years were studied. Significant decreases in total and integrated HIV-1 DNA were observed during the first 15 months of suppressive therapy before the concentrations became stable. Clonal analysis of HIV-1 pol demonstrated that the proportions of resistance mutations in DNA sequences after 2 years were lower than those in baseline DNA and RNA sequences. The changes in the clonal composition of HIV-1 env populations in three patients with evidence of changes in HIV-1 pol populations indicated a shift from predominantly R5-like viruses to predominantly X4-like viruses in two patients and the persistence of predominantly X4-like viruses in the third. Our analyses indicate the reemergence of ancestral sequences from long-lived cells or the residual production of wild-type virus from anatomic sites with limited access to antiretroviral drugs and the preferential infection of cells expressing CXCR4.