Phosphatidylcholine (PC) and licensed formulations containing PC were tested for their influence on the proliferation and viability of cells permanently infected with HIV-1 (human immunodeficiency virus type 1). PC alone, as well as pharmaceutical formulations containing PC, selectively inhibited the growth of productively infected lymphoid cells. The strongest growth inhibition was observed with formulations containing PC, glycerol and triglyceride together. The growth inhibition was dose-dependent for HIV-1-infected cells. Additionally, PC-containing formulations dramatically reduced antigen production from peripheral blood mononuclear cells (PBMCs) infected in vitro with HIV-1. In vivo experiments with Rauscher-MuLV-infected mice showed that PC administered either intraperitoneally or orally was able to inhibit Rauschervirus-induced splenomegaly. PC-containing formulations are currently used in man for supportive therapy at doses, which in vitro induced 50% growth inhibition of HIV-1-infected cells in vitro. Such doses have been used in man without side effects for many years. Thus, PC-containing formulations may be valuable for the treatment of HIV-1-infected individuals.