To understand the importance of autoimmunity in the development of type 1 diabetes in Taiwanese children, we evaluated the presence of β-cell autoantibodies and their correlation with residual β-cell function. Methods: From 1989 to 2006, 157 Taiwanese children with newly diagnosed type 1 diabetes were enrolled in this study. We determined the presence of β-cell autoantibodies, such as glutamic acid decarboxylase autoantibodies (GADAs), insulinoma antigen 2 autoantibodies (IA-2As), and insulin autoantibodies (IAAs). A 6-minute glucagon test was also performed at diagnosis. Results: At diagnosis, 73% of children tested positive for GADAs, 76% for IA-2As and 21% for IAAs. Ninety-two percent of them had at least one of the β-cell autoantibodies detected. Positivity for IAAs was more frequent in patients younger than 5 years than in those older than 5 years (45% vs. 13%). Using multiple regression analysis, the presence of GADAs or IAAs, or age of onset of these patients was an independent factor for residual β-cell function. Younger patients and those with GADAs had less residual β-cell function at disease onset, whereas those with IAAs had more insulin reserve. Conclusion: Autoimmunity plays an important role in the pathogenesis of type 1 diabetes in Taiwanese children, and the presence of IAAs tends to be more common in younger children.