To estimate the prevalence of metabolic syndrome using international dietetics federation (IDF) versus National cholesterol education program; adult treatment panel III (NCEP-ATPIII) definitions in Turkish adults. A cross-sectional study was conducted on a total of 1531 (male 758 and female 773) Turkish adults, aged between 20 to 64 years. Subjects were randomly selected from the general population of Ankara. The overall prevalence of MetS, as defined by NCEP-ATPIII and IDF was 48.2 and 56.4%, respectively. The agreement between National cholesterol education program (NCEP) and IDF definitions was substantial (kappa: 0.79). The prevalence was increased significantly according to increasing age in women, but was not different by age group in men. The prevalence of MetS in all age groups was higher in women. Hypertriglyceridemia and low High-density lipoprotein cholesterol (HDL-C) were the criteria of metabolic syndrome (MetS) with the highest prevalence. According to IDF criteria, the frequency of participants with high fasting plasma glucose (FPG) and Waist circumference (WC) was higher than the participants with adult treatment panel III (ATP III) criteria. The prevalence of the MetS was found to be very high, especially in women. The IDF definition resulted in a higher prevalence of metabolic syndrome than the NCEP-ATPIII in the entire Turkish population. The agreement between the IDF and NCEP definitions for metabolic syndrome was very good.