The pharmacokinetics and pharmacodynamics of intravenously injected biosynthetic human insulin (0.06 U/kg) and purified pork insulin, both regular, were compared intraindividually in ten presumably healthy volunteers. Some of the pharmacokinetic parameters, e.g., the area under the insulinemia curve, the total plasma clearance, and insulin bioavailability, were similar, whereas insulin biologic half-life appeared to be longer and the apparent volume of insulin distribution larger with BHI. No appreciable difference between the two insulins was observed as far as their hypoglycemic effect and secretory inhibition of endogenous insulin (expressed as C-peptidemia) were concerned, but reactive hyperglucagonemia was found to be less with BHI than with PPI. These findings are discussed in the light of our current knowledge of BHI.