The purpose of this study was to evaluate the effect of blood pressure (BP) rhythm on the values of Tp-Te interval and Tp-Te/QT ratio in patients with metabolic syndrome. Seventy patients with newly diagnosed hypertension who fulfilled the metabolic syndrome criteria according to the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (NCEP/ATP-III) were evaluated with 24-hour blood pressure holter monitoring. According to blood pressure rhythm, 35 patients with dipper blood pressure pattern and 35 patients with non-dipper blood pressure pattern were enrolled as two groups in our study. QT, corrected QT (QTc), Tp-Te interval and Tp-Te/QT ratio were measured from the 12-lead electrocardiogram. These parameters were compared between the groups. The nocturnal systolic and diastolic blood pressures were significantly higher in non-dipper patients than the dipper group. Baseline characteristics and QT, QTc intervals were similar in both groups. Tp-Te (91 +/- 12.24 vs 74 +/- 9.96; p < 0.001), Tp-Te/QT (0.24 +/- 0.027 vs 0.20 +/- 0.025; p < 0.001) and Tp-Te/QTc (0.22 +/- 0.023 vs 0.18 +/- 0.023; p < 0.001) were significantly increased in non-dipper group. These findings suggest that Tp-Te interval, Tp-Te/QT ratio end Tp-Te/QTc ratio were prominently increased in non-dipper hypertensive patients than dippers with metabolic syndrome.