Hybridization of DNA samples prepared from flow-sorted human chromosomes with a cDNA probe for the X-linked glucose-6-phosphate dehydrogenase (G6PD) suggested the existence of the G6PD-like locus on chromosome 17. Southern hybridization analysis of endonuclease-digested DNA samples from the human-mouse hybrid cell line with human chromosome 17, and from control human and mouse cells, proved that not only X chromosomes, but also chromosome 17, contain DNA sequences that are hybridizable with the G6PD cDNA probe. The G6PD-like locus on chromosome 17 could be a putative pseudogene or a functional gene for the fetal brain-specific G6PD isozyme or other protein.