Insulin-like growth factors (IGF) I and II are bound to high-affinity binding proteins in the blood circulation and other body fluids. These IGF-binding proteins are expressed at different concentrations in different tissues and are thought to regulate the activity of IGF I and II. Cloned cDNA for IGF-binding protein-1 (IGFBP1) has been used to verify the location of its gene to human chromosome 7 by Southern blotting to DNA from a human-mouse hybrid cell line. Further, by in situ hybridization the gene was regionally localized to 7p14-p12, and a Mendelian-inherited two-allele BglII restriction enzyme length polymorphism was identified, with the most frequent allele occurring in 53% of the chromosomes.