The human beta-globin gene is expressed--but the human fetal (gamma) and embryonic (epsilon) globin genes are not--in an induced mouse erythroleukemia cell line (M11-X) that contains most of human chromosome 11. A 24-hr exposure of M11-X cells to 5-azacytidine before induction causes "global" DNA hypomethylation but selective activation of the human gamma-globin genes. Genomic DNA is remethylated 2-3 days after exposure to 5-azacytidine, but sequences near the human and mouse globin genes remain hypomethylated, suggesting that the remethylation process is inhibited in these regions.