Purpose:The purpose of this study was to determine whether there is any difference in the clinical and laboratory characteristics of patients with autoantibody-positive and patients with autoantibody-negative type 1 diabetes at initial presentation. Methods:We analyzed 96 patients under 18 years of age with newly diagnosed type 1 diabetes. One or both of the pancreatic autoantibodies-glutamic acid decarboxylase autoantibodies (GADA) and insulin autoantibody (IAA)-were measured in all patients, and we reviewed clinical and laboratory characteristics according to the presence of these autoantibodies. Results:GADA was examined in 48 of 87 patients, and 55.2% of patients were positive. IAA was checked in 88 patients, and 39.8% were positive. Both GADA and IAA were measured in 83 patients, and 22.8% had both antibodies. The patients who had one or both autoantibodies (autoantibody-positive group) were younger than those not having any autoantibody (autoantibody-negative group). The autoantibody-positive group had lower BMI, corrected sodium level, and serum effective osmolarity, compared to the autoantibody-negative group (P<0.05). Similar differences were found between the GADA-positive and GADA-negative groups. However, there were no significant differences between the IAA- positive and IAA-negative groups. Conclusion:The prevalence of pancreatic autoantibodies was significantly higher in the under-6 years age group than in the other age groups. These findings suggest that measurement of autoantibodies at the initial diagnosis of diabetes is very useful for detecting immune-mediated type 1 diabetes and providing intensive insulin therapy, especially in younger children.