Clones of the K562 human erythroleukemic cell line have been isolated which can be transformed efficiently with recombinant DNA molecules carrying the bacterial Tn5 coded aminoglycoside phosphotransferase (aph) gene as a dominant selectable marker. Transformed cells are resistant to the drug geneticin. Recombinants carrying the human beta, delta and epsilon globin genes covalently linked to the aph gene have been introduced into these K562 cells using the calcium phosphate technique. Donor DNA molecules were present in multiple copies in the recipient cells. Expression of the human globin genes in the transformed K562 cells was found to be elevated in induced as compared to non-induced cells.