Latent collagenase was isolated by heparin-Sepharose affinity chromatography from the culture medium of clonally derived mouse osteogenic (MC3T3-E1) cells. Collagenase synthesis by MC3T3-E1 cells was significantly stimulated by the addition of parathyroid hormone to the serum-containing culture medium. The cellular origin of the isolated collagenase was confirmed by demonstrating the characteristic 3/4 and 1/4 fragments of collagen alpha-chain, as well as inhibition of the enzyme by anti-mouse bone collagenase antibody.