We have investigated the effect of exogenous IL-7 on replication of HIV-1 in PBMCs isolated from asymptomatic, chronically infected donors. We show that IL-7 induced virus replication and increased proviral DNA levels in CD8- PBMC cultures. IL-7 also increased the levels of doubly spliced HIV-1 tat RNA in these cultures. In comparison, IL-2 induced lower levels of virus production than IL-7, but had a more pronounced effect on cell proliferation. The IL-7-mediated increase in virus replication was not inhibited by neutralizing mAbs to IL-1 beta, IL-2, IL-6, or TNF-alpha, and was only partially dependent on ligation of the T cell accessory molecule CD28. CD8+ cells inhibited the increase in viral replication following IL-7 stimulation, but did not prevent virus replication following ligation of CD3 in the presence of IL-7. The data shows that IL-7 regulates HIV-1 replication in naturally infected PBMCs.