The clearance and the degradation of native pork insulin and human insulin prepared by recombinant DNA techniques (biosynthetic human insulin) were compared. Following intravenous injection in rats, biosynthetic human insulin was cleaved slightly more rapidly than pork insulin. Also in vitro, monoiodinated biosynthetic human insulin was degraded slightly more rapidly than pork insulin by the enzyme insulin protease. The apparent Km for pork insulin was 4.0 x 10-8 M and for the human product was 2.7 x 10-8 M. These results thus provide evidence for the integrity of the biosynthetic product.