A partial human cDNA clone for the iron-protein (IP) subunit of succinate dehydrogenase (EC 1.3.99.1) was used in Southern analyses of restriction enzyme digests of genomic human and hamster DNA as well as hamster-human hybrids containing a limited number of human chromosomes. The gene for this protein was mapped to human chromosome 1. Digestion of genomic DNA with several restriction enzymes yielded two fragments detectable on a Southern blot, in contrast to the expectations based on the sequence of the cDNA clone. A preliminary analysis of a genomic clone with most of the IP gene has indicated the presence of several introns containing restriction sites detected by the Southern analysis. This genomic clone was also used for subregional mapping by fluorescence in situ hybridization (FISH) to human metaphase chromosomes. A single locus in the region 1p35-36.1 was identified.