The human osteocalcin gene was assigned to chromosome 1 by Southern blot analysis of DNAs from a panel of mouse-human somatic cell hybrids with limited numbers of human chromosomes and the complete complement of murine chromosomes. By Southern blot analysis of DNAs from mouse-human hybrids that retain specific segments of human chromosome 1, we have determined that the locus of the human osteocalcin gene is on the long arm of chromosome 1, distal (telomeric) to the -spectrin gene. Osteocalcin is a bone specific protein and it is note worthy that another osteoblast product, the bone/liver/placental alkaline phosphatase gene has also been mapped to chromosome 1.