In this prospective analysis we investigated the clinical characteristics of black South African diabetic patients admitted to hospital with hyperglycaemic emergencies. The study cases were selected from the medical admissions to an urbanized, Johannesburg academic hospital over a period of 12 months. Only patients with severe diabetic ketoacidosis (DKA) or hyperosmolar non-ketotic hyperglycaemia (HNKH) as defined in the text were included. Over the study period, we identified 58 patients with severe DKA (M: 32, F: 26) and 24 with HNKH (M: 14, F:10). Thirty-two of the patients with DKA (55.2 %) were classified as having non-insulin dependent (Type 2) diabetes mellitus (NIDDM). Compared to the 26 subjects with insulin-dependent (Type 1) diabetes mellitus (IDDM), the NIDDM patients were older (51.7 vs 27.7 years) and had a significantly higher body mass index (BMI) (29.4 vs 23.5 kg m -2 , p = 0.002), and glucose levels 47.5 vs 34 mmol l -1 p = 0.004). Mortality from DKA was 6.8 % and from HNKH 16.6 %. Infection was the leading precipitating factor for both DKA and HNKH, followed by first presentation and noncompliance. We conclude that the majority of urban African patients admitted to hospital with DKA have NIDDM. Mortality from DKA among the black Africans in Johannesburg is low and comparable to the mortality in western Europe.