The time-action profile of the human insulin analogue B28Asp, which displays faster absorption rates from subcutaneous tissue compared to soluble human insulin, was studied under euglycaemic glucose clamp conditions (blood glucose 5.0 mmol l-1) in 14 healthy male volunteers. Subcutaneous injection of 0.15 U kg-1 body weight (range 9.5-14.3 U) of the insulin analogue or soluble human insulin resulted in half-maximal glucose infusion rates (after subtraction of mean baseline glucose infusion rates) that were reached significantly earlier after injection of B28Asp (45 +/- 11 (SD) min) as compared to human insulin (58 +/- 25 min, p < 0.05). Forty-five and 60 min after injection of human insulin, glucose infusion rates had increased by 3.4 +/- 1.8 and 4.8 +/- 2.3 mg min-1 kg-1 above baseline glucose infusion rates, reflecting 30 +/- 15 and 42 +/- 17% of maximal action of 10.6 +/- 2.7 mg min-1 kg-1. Following the injection of B28Asp, glucose infusion rates increased by 6.3 +/- 2.7 after 45 min and by 7.9 +/- 2.8 mg min-1 kg-1 after 60 min above baseline glucose infusion rates, reflecting 64 +/- 28% and 81 +/- 26% of maximal action of human soluble insulin (p < 0.001). Peak glucose infusion rates after injection of B28Asp were significantly higher and were reached earlier than after subcutaneous injection of soluble human insulin (p < 0.05 and p < 0.001). The human insulin analogue B28Asp showed a significantly faster onset of action as compared to soluble human insulin.