Insulin lispro is a newly developed analogue of human insulin where the positions of the amino acids lysine and proline have been switched at the end of the B chain of the insulin molecule. Insulin lispro with lysine at position B28 and proline at position B29 has a weaker tendency for self-association than human insulin. This leads to three major differences in the pharmacokinetics: the action begins faster, has a higher peak and the duration is shorter than with human insulin. Thus, insulin lispro has a more precise action profile for the mealtime than human regular insulin. Insulin lispro is recommended to be injected within 15 min before the meal in contrast to 30-40 min for human insulin. In clinical trials with insulin lispro, the postprandial rise of blood glucose is smaller, the rate of hypoglycaemia is lower particularly at night-time, the need for snacks is smaller and the patient preference is better than with human insulin. The long-term control as reflected by an improvement in the HbA1c level is better with insulin lispro than with human regular insulin, provided that an appropriate basal insulin regimen is used to take into account the shorter duration of action. A few patients have been described who have a severe resistance to human insulin but who have been successfully treated with insulin lispro. Insulin lispro was designed to be used as a mealtime insulin, and it is a step forward in the treatment of diabetic patients using a basal-bolus insulin regimen.