Aims: The relation of disease progression and age, serum interleukin 10 (IL-10) and interferon gamma (IFN¿) and their genetic correlates were studied in paediatric patients with newly diagnosed Type 1 diabetes. Methods: Two hundred and twenty-seven patients from the Hvidoere Study Group were classified in four different progression groups as assessed by change in stimulated C-peptide from 1 to 6 months. CA repeat variants of the IL-10 and IFN¿ gene were genotyped and serum levels of IL-10 and IFN¿ were measured at 1, 6 and 12 months. Results: IL-10 decreased (P