The metabolic syndrome (MetS) is represented by the co-occurrence of multiple metabolic and physiologic risk factors for both type 2 diabetes mellitus and atherosclerotic cardiovascular diseases. In spite of its high frequency and association with morbidity and mortality in the adult population, very little is known about its magnitude in the elderly and about the validity of the diagnostic criteria commonly used. The objective of this paper is to assess the prevalence rate of MetS and the validity of the Adult Treatment Panel III (ATP III) diagnostic criteria in an elderly Caucasian cohort, considering data from the Italian Longitudinal Study on Aging (ILSA), a population-based study with a sample of 5632 individuals aged 65-84 years at baseline (1992). Logistic regression models and ROC curve were used to test the validity of the cut off levels proposed. The prevalence of MetS was 31.5% in men, and 59.8% in women. The cut off levels suggested for both men and women by the ATP III panel indicated a significant association with the MetS for all components. Actually, the ROC analysis would suggest lower levels for glycaemia (106 mg/dl) in men, and higher levels for blood pressure in both men and women (145/95 and 135/90, respectively). Concluding, MetS is very common in the aged Caucasians and the diagnostic criteria proposed by the ATP III panel seem to be appropriate in older individuals. Small adjustments in the cut off levels could be suggested for glycaemia (men) and in blood pressure (men and women).