Cytoplasmic islet-cell antibodies (ICA) and endogenous insulin secretion were studied in 46 Sudanese children (mean age 11.6 years) with newly diagnosed insulin-dependent diabetes mellitus (IDDM). Islet-cell antibodies were detected both by the indirect immunofluorescence (IF) and complement fixation (CF) methods. Endogenous insulin levels were measured as C-peptide concentration using radio-immunoassays. The degree of metabolic control of diabetics was judged by the presence of diabetic ketoacidosis (DKA) at onset, glycated haemoglobin (HbA1c) level and insulin requirement, expressed as dose per kg body weight per day, at the time of presentation. Twenty-nine patients (63%) had either IF-ICA or CF-ICA or both in their sera. These figures are significantly higher than those reported for African populations. Islet-cell antibody positive patients had significantly lower C-peptide concentration, higher HbA1c level, higher insulin requirement and higher prevalence of ketoacidosis at presentation. Furthermore, the C-peptide levels were higher in CF-ICA positive patients than in subjects who showed only IF-ICA positivity. Our findings show a clear association between ICA and severity of diabetes at clinical onset and also suggest that the presence of CF-ICA at or shortly after diagnosis of IDDM is indicative of preservation of some functioning beta-cell mass.