A cDNA corresponding to the beta-subunit of the human fibronectin receptor (beta-FNR) was used as a probe in Southern blot analysis of mouse/human somatic cell hybrid DNAs and in in situ hybridization to metaphase chromosomes. The beta-FNR cDNA detects sequences present on human chromosome 10 as well as recognizing homologous sequences in the genome of the mouse parent of the somatic cell hybrids. In situ hybridization refined the localization of human sequences reacting with the beta-FNR cDNA to 10p11.2. The A-1A5 monoclonal antibody which recognizes the beta-subunit of the fibronectin receptor on the cell surface was used to confirm that the sequences present on chromosome 10 correspond to those required for expression of beta-FNR.