Objective: The objectives of this study were to determine the prevalence of diabetes mellitus in Trabzon city, Turkey, using standardized diagnostic criteria, and to evaluate associated factors. Methods: A total of 3000 eligible study subjects were selected. Of those, 2646 subjects participated in the study. Individuals aged greater than or equal to 20 years were selected from their family health cards and were invited to the health station. Anthropometric and demographic data were obtained for each subject. Plasma glucose was measured by an autoanalyser. People without previously diagnosed diabetes were categorized according to WHO diagnostic criteria as follows. Diabetes: a fasting plasma glucose (FPG) greater than or equal to 140 mg/dl or 2-h plasma glucose greater than or equal to 200 mg/dl after a 75-g oral glucose load. Results: The overall prevalence of diabetes in those greater than or equal to 20 years of age was 6.0% (n = 160). Among diabetic subjects, 69 were newly diagnosed diabetes mellitus. Age, body mass index (BMI), systolic blood pressure (SBP). diastolic blood pressure (DBP) and FPG were higher in diabetic subjects than in non-diabetic subjects. The prevalence of diabetes showed significant association with increased age (P < 0.0001). The overall prevalence of obesity was 19.2%. The combined prevalence of both overweight and obesity was 60.6%. The prevalence of obesity was 27.4% among women and 10.7% among men (P < 0.0001). Prevalence of diabetes increased with degree of obesity (P < 0.0001). The rate of obesity in diabetic subjects was 35.6%. In the study population as a whole, the prevalence of obesity increased with age, being highest in the 50-59 years age group, but lower again in the 60 + age group. Prevalence of SBP greater than or equal to 140 mmHg was 12.0% and of DBP greater than or equal to 90 mmHg was 8.2%. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.