Insulin aspart (NovoLog®, NovoRapid®2), a rapid-acting human insulin analog, provides more rapid absorption than regular human insulin after subcutaneous administration.In most randomized, nonblind clinical trials in patients with type 1 diabetes mellitus, insulin aspart administered immediately before meals resulted in significantly lower mean glycosylated hemoglobin (HbA1c) levels than regular human insulin (usually administered 30 minutes before a meal). Insulin aspart also significantly improved postprandial glycemic control compared with regular human insulin. The efficacy of insulin aspart was similar to that of insulin lispro when administered to patients with type 1 diabetes mellitus via continuous subcutaneous infusion in a randomized, nonblind trial.Preliminary data from randomized, nonblind trials suggest insulin aspart had a trend towards lower HbA1c levels compared with regular human insulin in patients with type 2 diabetes mellitus.Biphasic insulin aspart (30% soluble [rapid-acting] and 70% protamine-bound insulin aspart [BIAsp30]) [NovoLog®Mix 70/30, NovoMix®302] generally provided significantly better postprandial glucose control than a similar mixture of biphasic regular human insulin (BHI30) in a randomized, nonblind trial in patients with type 1 or 2 diabetes mellitus. However, the long-term efficacy of BIAsp30 was similar to that of BHI30 after 2 years in a randomized, nonblind trial in patients with type 2 diabetes mellitus.Patients with type 1 or 2 diabetes mellitus reported greater treatment satisfaction with insulin aspart or BIAsp30 than with regular human insulin or BHI30.The overall incidence of hypoglycemia with insulin aspart was lower than, or similar to, that of regular human insulin. Moreover, insulin aspart tended to be associated with a lower occurrence of nocturnal hypoglycemia and severe hypoglycemic events than regular human insulin.Conclusion: The standard preparation of insulin aspart has the potential to better mimic the physiological response to meals than regular human insulin. Insulin aspart when combined with a suitable basal insulin improved overall glycemic control and led to a similar or lower number of hypoglycemic episodes compared with a similar regular human insulin regimen. Insulin aspart was generally as effective and well tolerated as insulin lispro when administered by continuous subcutaneous infusion in a single comparative trial. The efficacy of biphasic insulin aspart has been documented in a small number of trials. Both insulin aspart and biphasic insulin aspart provide for flexible and convenient administration. Insulin aspart is now well established as an effective and convenient means of providing glycemic control which offers clinical and practical advantages over regular human insulin.