A consecutive series of 78 children with transient asymptomatic glucosuria was studied and followed up for up to 7.3 years. The age at presentation was 0.9-17.6 (median 4.6) years. One third of the patients had random blood glucose levels of > 10.0 mmol/l (180 mg/dl). Five patients (6.4%) developed insulin-dependent diabetes mellitus within 2.1 years after the first incident of glucosuria. These patients presented with higher levels of glycaemia than others, and three out of five were positive for islet cell antibodies with a first-phase insulin response < 46 mU/l in all four studied. Of the remaining 73 children, 3 were positive for islet cell antibodies and 12/55 had a first-phase insulin response under 46 mU/l. The insulin response deteriorated in 3 but reverted to normal in 7 patients. CONCLUSION. For a child with transient glucosuria and with presence of islet cell antibodies and a subnormal first-phase insulin response, therapeutic attempts to prevent overt insulin-dependent diabetes mellitus should be considered.