Objective: Several studies have evidenced that hypertensive patients with severe left ventricular hypertophy have an increased incidence of malignant ventricular arrhtyhmia and sudden death. However arrhtyhmia risk in mild to moderate hypertrophy is uncertain. This study aims to investigate the risk of ventricular arrhythmias in hypertensive patients with mild to moderate hypertrophy and evaluate the role of noninvasive arrhtyhmia markers and ambulatory blood pressures. Methods: Ninety-nine hypertensive patients (35 male, mean age 57.3±9.6) without coronary heart disease were included the study. All subjects underwent an echocardiography for measurement of LV mass index (LVMI) and were classified in two groups; hypertrophic (LVH(+) n: 43) and nonhypertophic (LVH (-) n: 56). Ambulatory blood pressure monitoring, 24 hour ECG, signal averaged ECG, and 12 lead ECG were performed in each group seeking to identify the arrythmogenic risk. Results: Holter ECG showed that 20.1% patients had Lown class II and 12.1% patients had Lown class IVa-IVb arrhtyhmia (potentialy malignant ventricular arrhtyhmia; PMVA). PMVA incidence was significantly higher in hypertrophic groups (20.9%) compared to nonhypertrophic groups (6.5%) (p<0.05). Ambulatory systolic and diastolic blood pressures were similar in PMVA (+) and PMVA (-) patients. At least two parameters of ventricular late potentials were significantly higher in LVH (+) group (25.7%) compared to LVH (-) group (4.9%) (p<0,01). HRV parameters were not different between two groups. QTcd was significantly increased in LVH (+) than in LVH (-) patients (54.1±16.7 vs. 47.5±17.7 ms) (p<0.05) The frequency of PMVA was significantly higher in increased QTcd compared to normal QTcd (24.3%-3.4%; p<0.01) and LP(+) patients (16.2%) compared to LP (-) patients (8.7%; p<0.05). Conclusion: Our data suggest that hypertension may be associated with high risk of PMVA in patients with mild to moderate LVH particularly in presence of LP and QTcd>50 ms. QTcd and at least 2 factors of LP were increased in mild to moderate LVH. Arrythmogenecity does not seem to be related with autonomic dysregulation and ambulatory blood pressure level in hypertensive patients.