We conducted a preliminary community survey for diabetes in the Bo district of southern Sierra Leone. Five hundred and one subjects comprising 256 rural adults in two villages and 245 urban adults in Bo town were randomly selected and screened for diabetes using random capillary blood glucose according to WHO criteria. There were 6 diabetics, all in the urban area, giving a prevalence of 2.4% in the urban population, and 0% in the rural villages. The mean (s.d.) capillary random blood glucose (RBG) concentration was 5.7 +/- 1.7 mmol/l for the entire study population, while concentrations for the urban and rural populations were 5.8 +/- 2 and 5.5 +/- 1.4 mmol/l respectively (P > 0.05). RBG increased significantly with age. The mean (s.d.) body mass index (BMI) was 22.3 +/- 4.9 kg/m2 for the total population while those for the urban and rural populations were 23.0 +/- 5.8 and 21.6 +/- 3.6 respectively (P < 0.01). Only 5% of the population were obese, i.e. BMI > or = 30 kg/m2. Dietary habits were similar in both town and country. According to this survey, the prevalence of diabetes is very low in rural Sierra Leone, but urban areas may be experiencing increasing prevalence. Mechanisms for effective screening and promotion of proper diet and exercise must be incorporated into existing health services to prevent an escalation of diabetes in urban Sierra Leone.