Background: Most patients diagnosed with diabetes mellitus < 35 years will have type 1 diabetes (T1D). The increase in youthonset type 2 diabetes (T2D) parallels the obesity epidemic and in African subjects ketosis-prone type 2 diabetes (KPD) may occur in this age group. Objectives, setting and subjects: To evaluate the clinical, biochemical and immunologic characteristics of patients diagnosed with diabetes < 35 years presenting to a tertiary diabetes clinic in Durban, South Africa over 13 years. Design: A retrospective chart review of patients < 35 years diagnosed with diabetes was conducted. Data included clinical and laboratory variables, complications and follow-up status. Results: The study included 517 patients of whom 445 (86.1%) were diagnosed with T1D, 27 (5.2%) with T2D, 27 with KPD (5.2%) and 18 (3.5%) with other forms of diabetes. Mean age of the total group was 28 ± 10 years. Subjects with T1D were younger at diagnosis with a lower BMI than both T2D and KPD. HbA1c was higher in subjects with T1D. Overall mortality was low (3.5%) and follow-up was poor in all groups. Conclusion: The majority of young people with diabetes in KwaZulu-Natal, South Africa, have T1D, with small numbers of other types. Glucose control is poor with a high loss to follow-up.