The prevalence and associated factors of diabetes mellitus (DM) and impaired glucose tolerance (IGT) were studied in a tribal community with an apparently high diabetes prevalence. A sample of 724 subjects aged > or = 25 years was selected using a multi-stage cluster method and underwent a 75 g oral glucose tolerance test. The crude prevalence of DM and IGT were 8.3% (men 9.9%; women 7.5%) and 7.9% (men 4.1%; women 9.7%), respectively. Age-adjusted prevalence rates, according to the standard population of Segi, were 10.4% (95% CI 7.7-13.2) and 9.8% (95% CI 7.2-12.5) for DM and IGT, respectively. No urban/rural differences were found in the prevalence rates of DM and IGT. New cases (5.1%) were almost twice as common as previously known cases (3.2%). Family history of diabetes, obesity, and advanced age were associated with higher rates of diabetes. The results confirmed that diabetes is common in the Danagla community compared to other communities of northern Sudan. Varying environmental, nutritional, and genetic factors may contribute to this high prevalence. These findings will have profound impact on the health services for this community and the Sudan as a whole.