Objective: To determine prevalence of the metabolic syndrome (MS) in a sample representing Turkish population using United States Adult Treatment Panel-3 guidelines. Design: The study included random samples from both urban and rural populations in the seven geographical regions of Turkey. The population for this analysis were 2108 men (1372 in urban and 736 in rural areas) and 2151 women (1423 in urban and 728 in rural areas) with a mean age of 40.9714.9 years (range 20-90). Results: The prevalence of the MS diagnosed using the Adult Treatment Panel III criteria was 33.9% (1442 of 4259) and differed significantly in men (28%) and women (39.6%). The prevalence of syndrome increased with age in men, from 10.7% in subjects aged 20-29 years to 49% in those aged over 70 years. The prevalence increased with age in women, from 9.6% in subjects aged 20-29 years to 74.6% in those aged 60-69 years, and decreased to 68.6% in those over 70 years of age. The prevalence of the syndrome was similar in urban (33.8%) and rural (33.9%) population. We found 26.8, 26.4, 19.3, 10.9 and 3.6% of the population had at least 1, 2, 3, 4 or 5 components, respectively. We found 57.2, 32.3 and 10.6% of the subjects with MS had 3, 4 and 5 components, respectively.