Serum lipids and lipoproteins were measured in 157 insulin dependent diabetic children and adolescents (IDDM) and in 350 healthy reference individuals. Serum triglyceride values were lower and total cholesterol and high density lipoprotein cholesterol higher in IDDM. Metabolic regulation reflected by glucosuria, postprandial blood glucose, number of hypoglycemic episodes and hemoglobin A1c all correlated strongly with serum triglyceride and very low density lipoprotein cholesterol. Serum lipids and lipoproteins did not correlate with obesity. Three children had genetic hyperlipoproteinemia. In IDDM measurement of serum lipids and lipoproteins can thus be used to further assess metabolic regulation. Measurement of serum lipids and lipoproteins seems warranted for future evaluation of the risk of cardiovascular disease in IDDM.