This paper presents the results of a study that aimed to describe the prevalence and evolution of metabolic syndrome (MetS) in the Mediterranean population of Catalonia, Spain, between 1992-1993 and 2002-2003 by applying the National Cholesterol Education Program's Adult Treatment Panel III (ATPIII) and International Diabetes Federation (IDF) definitions. Data from two cross-sectional population-based surveys were used (ENCAT 1992-1993 [n = 820] and 2002-2003 [n = 1,384]). Applying IDF definitions, MetS tended to increase (P = 0.08), from 25% in 1992-1993 to 28.5% in 2002-2003. Applying ATPIII definitions, MetS prevalence was lower, and it increased significantly (P < 0.001) from 18.4% in 1992-1993 to 24.8% in 2002-2003. MetS prevalence is high and has increased significantly in the last decade in Catalonia.