To assess pharmacokinetics and biological activity of the new L-SNC insulin (Berlin-Chemie, a low immunogenic pork insulin in neutral solution purified by chromatography) ten healthy male subjects were connected to the BIOSTATOR. After an overnight fast 0.4 U of L-SNC insulin per kg body weight were injected subcutaneously in the thigh of each individual. Plasma insulin concentrations rose gradually reaching their maximum values after 8 hours. According to C-peptide levels there was some inhibition of endogenous insulin secretion. For the evaluation of insulin action we used the closed loop system (BIOSTATOR) which was transformed in its function into a glucose controlled dextrose infusion system. The amount of glucose delivered by the BIOSTATOR in order to maintain blood glucose steady state concentrations at the "basal" level was taken as a measure of biological activity of the injected insulin. The glucose infusion rate increased after insulin administration, reaching statistical significance after 3 hr. The maximum effect of L-SNC insulin was observed between 5 and 12 hours after injection. The overall duration of action of more than 16 hours meets the increasing need for insulin in the early morning in many diabetic patients. Therefore, L-SNC insulin should be recommended for intensified conventional insulin therapy to cover the night and to prevent dawn phenomenon in insulin dependent diabetics.