Based upon a 3-week observation at a summer camp for diabetic children whose medical therapy, metabolic rate, diet, physical exercise and special training could be closely monitored, the following parameters were measured at the beginning and at the end: In whole blood and young erythrocytes HbA1, in serum triglycerides, cholesterol, HDL-cholesterol, as well as apolipoprotein A and B. From these data, the LDL-cholesterol and the atherosclerosis indices (LDL-cholesterol/HDL-cholesterol and apolipoprotein B/apolipoprotein A) were determined. The following results were obtained: the parameters of lipid-metabolism recognized as risk factors for vascular complications such as triglycerides, cholesterol, LDL-cholesterol and apolipoprotein B, were the same as those obtained from a control group of healthy children in the same age. Using HbA1 as the basis for the observations, the risk factors were reduced by normalisation of glucose metabolism. On the other hand, the apolipoprotein A and HDL-cholesterol, well known as protective factors against atherosclerosis, are higher than in the control group and show a further increase with metabolic normalisation. The conclusion is: If medical therapy, metabolic rate, diet, physical exercise and special training are better controlled, the risk of diabetes developing macroangiopathy can be diminished.