The occurrence and risk factors of severe hypoglycemic attacks were analyzed during a 4-year study in a group of children and adolescents who received human insulin and followed a multiple daily injection regimen (three or four injections per day); 29 patients experienced severe hypoglycemia at least once in 4 years. Of these, 13 suffered recurrent episodes: 8 had two episodes, 4 had four episodes, and 1 patient had seven episodes. For comparative purposes, the nonhypoglycemic population (217 diabetic children) was used as a control group. The hypoglycemic children received insulin doses which were significantly higher than for nonhypoglycemic patients (1.05 +/- 0.6 U/kg daily vs 0.87 +/- 0.7; P < 0.05). Moreover, the hypoglycemic group had a significantly higher mean number of previous episodes of severe hypoglycemia than the nonhypoglycemic group (0.98 +/- 1.2 vs 0.26 +/- 0.7; P < 0.001). There was no significant difference in age, sex, duration of disease, and metabolic control between hypoglycemic and nonhypoglycemic children. There was no association between severe hypoglycemia and the presence of retinopathy, persistent microalbuminuria, or autonomic neuropathy. Severe hypoglycemia is a recurrent problem, not related to the quality of metabolic control nor to the presence of long-term microvascular complications, and diabetic children with a personal history of severe hypoglycemia are at risk for future episodes.