The objective of this study was to investigate the association between sodium intake and metabolic syndrome (MS) in individuals free from the confounding effects of increased blood pressure (BP). In all, a total of 1655 individuals (45.8% men) who participated in the MONICA-WHO/Vitoria Project, mean age 45+/-11 years were investigated. According to NCEP-ATP lll criteria, MS prevalence was 32.9 and 85% of these individuals had BP >130/85 mm Hg. Thus, high BP represents the main MS risk factor. Twelve-hour nocturnal urine (1900 to 0700 hours) was used to measure urinary sodium and potassium excretion. Sodium excretion was associated with BP. From the optimal BP level up to stage lll hypertension, the mean (median) sodium excretion increased from 99 (89) to 128 (134) mEq and from 81 (69) to 112 (103) mEq in men and women, respectively (P<0.001 for trend; median). However, when 781 individuals with BP <130/85 mm Hg (including 80 drug-free normotensive individuals with MS) were stratified according to the gender and number of MS components, no significant differences were observed either in the urinary volume or in the sodium or potassium excretion. For each of the four MS components, sodium excretion was 96+/-48, 97+/-53, 108+/-65 and 97+/-49 mEq for men, and 83+/-51, 83+/-58, 80+/-49 and 93+/-45 mEq for women, respectively. No differences were found in urinary sodium excretion in normotensive individuals, regardless of the presence of MS. Therefore, it seems that high sodium intake is not an MS predictor per se as suggested earlier.