The occurrence of diabetes mellitus is increasing throughout the world, both in industrialised nations and in developing countries. While this disease is not a leading cause of death in developing country populations, it must nevertheless be considered for its social and economic impact. This study examines the clinical and epidemiological situation of diabetes mellitus in the city of Kinshasa, Democratic Republic of Congo, as based on data from two city hospitals: Saint Joseph's Hospital (SJH) and the Centre Hospitalier Monkole (CHM), two urban health facilities typical of those developing countries. The results show that diabetes is a real public health problem in Congo. Average blood glucose levels were above 300 mg/dl in 44.4% of patients at SJH and 41.5% at CHM, and hypertension (> or = 140/90 mmHg) was reported in 35.8% of patients at SJH and 20% at CHM. The management of diabetes and, in particular, its complications is suffering because of some cultural influences but mainly economic ones. In fact, incidence of disease complications is closely linked to the financial status of patients and facilities. SJH, which serves mainly the low-income community, has a greater incidence of severe diabetes-associated complications than CHM, which treats patients with a higher mean income level. SJH hospitalised patients had a 24.7% incidence of diabetic foot with 3 amputations as compared to only a 10% incidence and no amputations for CHM hospitalised patients. At SJH, 17.3% of patients died during the study, while at CHM none died. Overall, differences in the prevalence of complications between SJH and CHM patients were found not to be significant. For the large majority of Congo population, education on diabetes is not available, and due to the failure of the national health system, access to treatment is impossible. Furthermore, because most diabetic people in Congo go untreated, the mortality rate for the disease is high. Congo would greatly benefit from a national diabetes program in order to give all diabetic patients in Congo access to good and consistent medical care.