OBJECTIVE: To compare characteristics of autoantibody (aAb)-positive and -negative cases of type 1 diabetes (T1D) <18 years old in the T1D Exchange clinic registry. METHODS: An aAb-positive status (n = 6239) required at least one of the aAbs to be positive; an aAb-negative status (n = 485) required negative results on testing of at least two different aAbs. RESULTS: The percentage of males was higher (58% vs. 51%; P = 0.002) and total daily insulin dose lower (P = 0.003) in aAb-negative compared with aAb-positive groups, but both groups had similar distributions of race-ethnicity, diagnosis age, family history of T1D, ketoacidosis at diagnosis, body mass index at diagnosis and at most recent office visit, and current HbA1c. CONCLUSIONS: Male gender and lower total daily insulin dose were more likely in aAb-negative than aAb-positive children with T1D, but no other distinguishing characteristics were identified. Further examination of characteristics of aAb-negative cases may help characterize the heterogeneous nature of T1D.