The chromosomal location of mouse leukocyte-interferon (IFN-alpha) genes was determined by Southern blot analysis of DNA from a panel of Chinese hamster x mouse somatic cell hybrids using a mouse IFN-alpha cDNA as a hybridization probe. All resolvable mouse genes are located on mouse chromosome 4. In addition, two common restriction site polymorphisms within these genes were identified in several mouse strains.