Zinc human insulin (recombinant DNA) or zinc PPI (Monotard) 20 U was injected subcutaneously to study the time-action profile in six healthy volunteers. During the test period they received a 10-g biscuit containing 3% moisture, 7% protein, 10% fat, 80% carbohydrate, and 30 ml of water every hour. The onset of action with zinc human insulin occurred earlier than with zinc PPI. Also, the intensity of the blood sugar-lowering effect was more pronounced 3 and 4 h after administration of insulin. No other statistically significant differences were detected between the two blood glucose curves. The results show that it is possible to develop a zinc human insulin formulation with a duration of the blood sugar-lowering effect equal to a zinc PPI formulation, DIABETES CARE 5 (SUPPL. iy. 71-72, 1982.