The MAGE-1 gene encodes an antigen recognized on melanoma cells by autologous cytotoxic T cells. This gene shows a wide range of expression in many human tumors but not in normal tissues except for testes. We used reverse transcription polymerase chain reaction assays to analyze the expression of the MAGE-1 gene in two variants of an erythroleukemic cell line, K562. Comparison of two variants of the K562 cell line in different stages of differentiation showed different patterns of expression of the MAGE-1 gene. The more undifferentiated cell line (K562A) expressed high levels of specific MAGE-1 mRNA, in contrast to K562B, which features of erythroid differentiation, without MAGE-1 expression. Interestingly, we could not modulate MAGE-1 gene expression when in vitro differentiation of K562A was induced with Ara-C. Finally, our data indicate that MAGE-1 expression is not necessary for the maintenance of the transformed phenotype.