Abstract: This study examined the circadian variation of ventricular arrhythmias in hypertensive patients.104 patients with hypertension underwent continuous 24 hour Holter monitoring and ventricular arrhyhythmias were classified by 6-hour time intervals.The results showed that the frequency of ventricular arrhythmias during the 4 different time intervals was 40％,26％,19％,and 15％.A higher prevalence of complex or frequent ventricular arrhythmias was found in 6AM～12AM interval than in the other intervals.It is speculated that the morning increase in sudden cardiac death might be related to the increase in frequency of ventricular arrhythmias.