A novel method involving the packaging of phage particles was used to introduce cosmids containing components of the human beta-globin locus control region (LCR) and the human (A)gamma, delta, and beta globin genes into mouse erythroleukemia (MEL) cells. After stable transfection, MEL clones were selected and analyzed for expression of human genes. Both (A)gamma and beta globin mRNA were expressed in these clones, indicating that MEL cells do not suppress transcription of the human gamma globin gene. The variability of human (A)gamma vs. beta globin expression from clone to clone prevents a clear delineation of differences in the expression of these two genes with a cosmid in which a region potentially involved in gamma-to-beta switching has been deleted. The results suggest that MEL cells are capable of supporting human gamma expression, despite their predominantly adult phenotype.