A cross-sectional study was performed involving epidemiological and clinical features of the metabolic syndrome (MS) in Spanish migrants to Brazil and their descendants. This included 479 subjects: Group A (Spanish migrants): n=215; Group B (descendants born in Brazil of Spanish parents): n=126, Group C (mixed descendants born in Brazil with either father or mother born in Spain): n=138. MS was defined according to the original NCEP/ATP III criteria and by the revised NCEP/ATP definition (glucose>or=100mg/dl). Overall prevalence of MS according to NCEP/ATP III criteria was 26.3%. Age/sex-adjusted prevalence was 27.4%. When the revised NCEP criteria were considered, overall prevalence was 30.1% (age/sex-adjusted 31.3%). The differences between the two criteria were 3.8% and 3.9% (CI -1.9-9.4%). When stratified by groups the MS was more prevalent in Group A (37.2%) and Group B (20.6%) than in Group C (10.9%). Environmental factors may have influenced the development of MS. Reason for the apparently protective role of genetic features due to admixture between populations in the mixed descendants needs to be explored.