The aim of the study is to assess the prevalence of metabolic syndrome (MetS) in Spain using specific cutoff points for waist circumference (WC) (>94.5 cm for men and >89.5 cm for women) and evaluating the influence of several socio-demographic and economic factors. Data on MetS were obtained from a national study of 4,727 subjects from 18 to 90 years of age, conducted in Spain between 2009 and 2010 (The firstname.lastname@example.org study). MetS was defined applying the new Harmonized definition (evaluating the use of abdominal obesity (AO) as a obligatory criterion for MetS or not) as well as with other widely used criteria. Results were then compared with data from previous studies. Multiple logistic regression models were used to evaluate the influence of different social factors. The age-standardized MetS prevalence was 38.37 % (CI 35.74–40.99) in men and 29.62 % (CI 27.56–31.69) in women, when AO was required as a diagnostic criterion; 42.13 % (CI 39.37–44.89) and 32.31 % (CI 30.15–34.47) in men and women, respectively, if AO was not considered mandatory. Prevalence of MetS increased with age (p < 0.001 for trend). Women with a lower educational level were more likely to have MetS (OR 4.4; 95 % CI: 2.84-6.7) as compared with those with a higher educational level. Subjects with MetS had a worse physical quality of life. The combination of AO, hypertension and carbohydrate alterations was the most common MetS’ pattern. A high prevalence of MetS was detected in the Spanish population especially in men, the elderly and women with a low educational level.