Mybl2 encodes a transcription factor that is thought to play an important role in cell cycle progression. Here we report the chromosomal localization of Mybl2 in mouse and human. Using mouse Mybl2 cDNA clones as probes, we assigned Mybl2 in an interspecific backcross panel to distal Chromosome 2. Using human cDNA probes in combination with FISH analysis, we localized MYBL2 to chromosome 20q13.1, a region that is commonly deleted in myeloid disorders. Both chromosomal regions are highly homologous, and the map positions, therefore, confirm each other. However, our findings are in contrast to a previous report by Barletta et al. (Cancer Res. 51:3821-3824, 1991) that placed the MYBL2 gene on human chromosome Xq13.