Efficient transfer of the beta-globin gene into primitive hematopoietic progenitors was achieved with consistent and significant expression in the progeny of those cells. Retroviral vectors containing the intact genomic human beta-globin gene and the neomycin (G418)-resistance (neoR) gene were constructed. These gave titers of 10(6) or more neoR colony-forming units/ml when packaged in psi 2 cells. Mouse bone marrow cells were infected by coculture with producer cells and injected into lethally irradiated animals. Several parameters were varied to enhance infection frequency of colony-forming units, spleen (CFU-S); overall 41% of 116 foci studied contained an intact proviral genome. The human beta-globin gene was expressed in 31 of 35 CFU-S-derived spleen colonies that contained the intact vector genome at levels ranging from 1% to 5% of that of the mouse beta-globin genes. Infected bone marrow cells were also injected into genetically anemic W/Wv recipients without prior irradiation. Human beta-globin chains were detected in circulating erythrocytes by immunofluorescent staining with a specific monoclonal antibody. All animals injected with donor cells that had been cultured in G418 (1 mg/ml) for 48 hr after retroviral infection had circulating erythrocytes containing human beta-globin chains between 3 and 8 weeks after transplantation.