OBJECTIVE: To examine the prevalence of metabolic syndrome (MS) and its associated risk factors in Mexican adults aged 20 years or older, using data derived from the National Health and Nutrition Survey 2006 (ENSANUT 2006). MATERIAL AND METHODS: The ENSANUT 2006 was conducted between October 2005 and May 2006. Questionnaires were administered to 45 446 adult subjects aged 20 years or older who were residents from urban and rural areas. Anthropometric and blood pressure measurements were obtained from all subjects and fasting blood specimens were provided by 30% of participants. We randomly selected a sub-sample of 6 613 from which laboratory measurements were carried out for glucose, insulin, triglycerides, total cholesterol and HDL-cholesterol. For this analysis, we included only results from eight or more hours of fasting samples (n=6 021). We used individual weighted factors in the statistical analysis and considered the survey's complex sampling design to obtain variances and confidence intervals. All analyses were done using SPSS 15.0. RESULTS: In accordance with definitions by the National Cholesterol Education Program Adult Treatment Panel III (ATP III), the American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI), and the International Diabetes Federation (IDF), the prevalence of MS in Mexican adults aged 20 years or older was 36.8, 41.6 and 49.8%, respectively. Women were more affected than men due to the higher prevalence of central obesity among females. Prevalence of MS increased with age and was higher among populations living in metropolitan areas, in the west-central region, and those with lower education. DISCUSSION: Regardless of the MS definition, a large proportion of Mexican adults has the condition, so preventive measures are needed to decrease the prevalence of the MS components in this population. MS can predict type 2 diabetes and cardiovascular disease, two of the main causes of death in the adult population in Mexico. The intentional search of MS components allows stratifying the population according to risk levels. Treatment for each component should be implemented properly to prevent or delay onset of type 2 diabetes and cardiovascular disease.