Prolongation of P-wave durations and increased P-wave dispersion are independent predictors of atrial fibrillation (AF). AF is the most common arrhythmia of the general population. Prehypertension, including those with systolic blood pressure ranging from 120-139 mmHg or diastolic blood pressure ranging from 80-89 mmHg was described by JNC7. Prehypertension is the predictor of development of hypertension in the future. Prehypertension is associated with excess cardiovascular morbidity and mortality. In this study, we evaluated relationship between prehypertension and P-wave dispersion.Seventy-eight prehypertensive patients (group 1: mean age 44.6+/-11.2 years; 45 male) and 78 normotensive patients (group 2: mean age 43.3+/-7.0 years; 43 male) were enrolled in this study. Standard 12-lead ECGs were recorded in all patients using a paper speed of 50 mm/s. In all patients, transthoracic echocardiographic examination was performed.Pmax and P-wave dispersion were significantly higher in group 1 compared with group 2 (103.59+/-19.8 ms vs 93.59+/-13.4 ms, p<0.001; 50.51+/-18.6 ms vs 39.85+/-10.6 ms, p<0.001, respectively).Pmax and P-wave dispersion increase in prehypertensive patients compared with normotensive patients. This data might show increased risk of AF in prehypertension.