We have determined the complete sequence of the cDNA clone representing the full size human skin collagenase mRNA. Collagenase is synthesized in preproenzyme form, Mr 54,092, with a 19 amino acid long signal peptide. The primary secretion products of the enzyme consist of a minor glycosylated form, Mr 57,000, and a major unmodified polypeptide of predicted Mr 51,929. Proteolytic activation of human skin procollagenase results in removal of 81 amino acid residues from the amino-terminal portion of the proenzyme. Both potential N-glycosylation sites are contained within the proteolytically activated form of the enzyme. The primary structure of the coding region of the presented clone is homologous to an oncogene-induced rat protein whose function is still unknown, although preliminary observations suggest that it is not rat skin collagenase.