We have recently characterized cDNAs and genomic DNA fragments for human type I cGMP-dependent protein kinase (cGK). By probing human × hamster hybrid cell lines with a 1.2-kb intron fragment from the human type I cGK gene, we identified a 5.9-kb BgIll restriction fragment and localized it·human chromosome 10. In situ hybridization analyses using 3H-labeled cDNA and genomic DNA probes for the human type I cGK to human metaphase chromosomes supported the somatic cell hybrid data and indicated that the gene (PRKGIB; protein kinase, cGMP-dependent) maps to 10p11.2-→q11.2.