Pharmacokinetic and pharmacodynamic properties of a rapid-acting analog of human insulin, insulin aspart, were compared with those of soluble human insulin in Japanese healthy subjects. Subcutaneous single injections (0.025 and 0.05 U/kg body weight (BW)) of insulin aspart produced a significantly earlier peak of exogenous insulin level in comparison with human insulin (30.8+/-13.8 versus 61.3+/-14. 6 min, P<0.9001 for 0.025 U/kg; and 39.2+/-18.8 versus 99.2+/-53.8 min, P<0.005 for 0.05 U/kg). The peak serum level of insulin aspart was higher than that of human insulin (23.0+/-6.0 versus 9.9+/-3.1 microU/ml for 0.025 U/kg; and 30.9+/-9.2 versus 13.3+/-4.1 microU/ml for 0.05 U/kg, P<0.0001). The time to the minimal level of glucose after insulin aspart was significantly shorter compared with human insulin (P<0.05 for 0.025 U/kg BW and P<0.01 for 0.05 U/kg BW). The Delta change in blood glucose induced by insulin aspart was larger than that observed for human insulin at any dose (P<0.001). The repeated injection of insulin aspart before each meal also resulted in a rapid rise in exogenous insulin level with peak level obtained approximately 40 min after insulin aspart at any dose. When compared with results of other trials with insulin aspart, the present results showed that pharmacokinetic and pharmacodynamic profiles of the rapid-acting analog insulin aspart in Japanese subjects are no different from those in nonJapanese subjects.