Sixty-five percent of acute myeloid leukemias subtype M2 (AML-M2), displaying a translocation between chromosomes 8 and 21 (t8;21) have also lost one or other copy of the sex chromosomes (XO). This finding has led to the hypothesis that a recessive oncogene may be present in the DNA common to both sex chromosomes, that is the pseudoautosomal region. The alpha chain of the receptor for the hemopoietic growth factor GM-CSF has recently been mapped to the human pseudoautosomal region and, given the role of this molecule in the control of normal hemopoiesis, it is thought to be a good candidate gene. This paper examines the structure, expression, and sequence of the GM-CSF receptor alpha chain gene (GMR alpha) in three primary AML-M2,XO samples and one AML-M2,XO cell line. Results of this work show no gross rearrangement or loss of the remaining allele of GMR alpha, detectable expression of its transcript and protein, and no changes at the nucleotide sequence level. Thus, we find no evidence to support a role for the GM-CSF receptor alpha chain molecule in the development of AML-M2,XO leukemias.