Objective:To investigate the relationship between day and night regularity of asymptomatic ventricular premature contraction (VPC) and the activity of autonomic nervous system and its clinical significance. Methods: Thirty children with the absence of underlying organic heart disease were examined with 24 hour dynamic electrocardiogram (DCG)

the function of autonomic nervous system and ventricular late potentials (VLP).Results:The rate (43%

13/30) was the day type VPC

12 out of the 13 resulted from increased activity of sympathetic nerve .The rate (30%

10/30) was the night type VPC

all of them resulted from the activity of the vagus nerve enhanced. There was a positive correlation between VPC frequency of day type and heart rate (r=0.67

P<0.05) and a negative correlation between VPC frequency of night type and heart rate (r=-0.69

P<0.05). 20 out of the 30 cases were examined by VLP. All of them were normal. Conclusion:Asymptomatic VPC of day type possibly resulted from increased activity of sympathetic nerve. However

asymptomatic VPC of night type could be related to the activity of the vagus nerve enhanced. The type asymptomatic VPC usually had a good prognosis.