Objective: Tyg index, a surrogate marker of insulin resistance, was shown to be a predictor of development of metabolic syndrome (MS) among diabetes patients and general population while the predictive value among young hypertensives is less known. The aim of the present study was to investigate the predictive capacity of tyg index for incident MS among young untreated hypertensives. Design and method: we investigated 949 young-to-middle age stage I hypertensives from the HARVEST study, mean age 32.4±8.7 years, mean BMI 24.7±3.2 kg/m2, 69.2% males, without MS at baseline. Mean 24h blood pressure (BP) at entry 130.0±10.9/81.0±8.3 mmHg. Tyg index was calculated according to the usual formula. Patients were divided into tyg quintiles:7.008-7.895, 7.896-8.199, 8.200-8.423, 8.424-8.585, >=8.586 respectively. The risk of MS was calculated by means of survival Cox analyses adjusted for several confounders. Results: Patients in the highest quintiles were significantly older 35.3±8.1 years and heavier 25.3±3.3 kg/m2 than the bottom ones (p<0.001). Also baseline metabolic parameters were worse in top quintile (serum glucose 96.2±14.1, uric acid 5.3±1.2 mg/dl, total cholesterol 212.1±35.3 mg/dl, HDL 51.8±10.2 mg/dl) in comparison to the lower ones (p<0.001 for all comparisons). Baseline 24h BP values did not differ according to Tyg quintile, while heart rate was higher in the top quintile (74.3±8.4 bpm, p<0.001). During 8.1 years of follow-up, 76.3% of subjects developed new onset MS. Again, metabolic parameters were worst in the highest tyg quintile (serum glucose 97.9±15.4 mg/dl, total cholesterol 225.9±44.7 mg/dl, and HDL 52.1±15.2 mg/dl, as was final BMI (26.2±3.6Kg/m2, p<0.001 for all comparisons). Final 24h BP did not differ according to Tyg quintile while heart rate was higher in the highest quintile (p<0.001). In multivariate Cox analysis patients in the 4th and 5th quintiles presented the highest risk of new onset MS (HR 1.51 (1.11-2.06) p=0.009; HR 1.46 (1.09-1.46)p=0.011, respectively), in comparison to the bottom quintile. Conclusions: The risk of development of metabolic syndrome was significantly increased among patients in the top tyg quintiles, confirming its predictive capacity as a surrogate marker of insulin resistance among young stage I hypertensives.