BACKGROUND: Type 1 diabetes develops due to the destruction of insulin-secreting beta-cells by an autoimmune process, in which both genetic and environmental factors are involved. In children with newly diagnosed type 1 DM, the prevalence of ICA (Islet cell cytoplasmic antibody) is 60~86% and is highest at the time of onset after which it decreases. But, GADA (glutamic acid decarboxylase anti- bodies) are characterized by substantial fluctuations in the humoral immune response over a long period after clinical manifestation. This study was performed to evaluate the persistence of type 1 DM associated autoantibodies, including ICA and GADA, and their relation to clinical characteristics of the disease after clinical manifestation. METHODS: Eighteen childhood onset type 1 diabetes patients (mean age 13.7 years; duration 3.9 years) were included in this study. ICA was measured by indirect immunofluorescence using conventional ICA-IgG and positive samples were titered by serial dilutions. Also the sera were screened for GADA by radioimmuno-assay. RESULTS: The positivities of ICA and GADA at the time of study were 55.6% and 61%, falling to 44.4% and 41.2% 5 years later, respectively. There was no case of an ICA negative patient becoming positive or whose ICA titer was increased later. One case of a GADA negative patient became positive later. Initial c-peptide levels didn't have any correlation with initial ICA titers or ICA prevalence, but did with initial GADA titer. There were significant correlations between initial GADA titer and ICA prevalence (p<0.001), and between initial GADA titer or ICA titer and later ICA persistence (p<0.05). CONCLUSION: ICA and GADA persisted long after the clinical diagnosis of type 1 diabetes. And the persistence of autoantibody positivity showed a weak relation with endogenous insulin secretion and clinical characteristics, both at and after diagnosis of overt type 1 diabetes.