A group of 58 diabetics, age 6-17 years and with a duration of diabetes of 3-14 years was studied in order to show whether the nature of the clinical manifestations and the treatment at the onset of the disease are related to the subsequent C-peptide production and also whether remaining C-peptide production is related to better diabetic control. The relations between a number of clinical and laboratory variables were analysed including the degree of ketosis and the insulin dose given at onset of diabetes, the incidence of postinitial remission period, the fasting C-peptide level after the remission period, the level of insulin antibodies and the actual diabetic control expressed as the degree of glucosuria in the patients' urine tests at home. Multiple regression analysis was the main method used. Postinitial remission was positively correlated to initial insulin dose and negatively correlated to duration of ketonuria at onset. C-peptide, which was found in 24.1% of the patients was positively correlated to age at onset and initial insulin dose, but negatively correlated to ketonuria at onset. Diabetic control was positively correlated to insulin dose at onset and to C-peptide level, but negatively correlated to insulin antibodies. It could further be shown that patients who had received a more vigorous treatment immediately at onset had both a higher incidence of postinitial remission and a better diabetic control. The results suggest that an early diagnosis followed by rapid normalization of the metabolism at the onset of juvenile diabetes increase the possibility of preservation of some of the endogenous insulin production, which seems to facilitate diabetic control.