Although nocturnal enuresis is probably the most common developmental disorder in children, the pathogenesis and management remain unclear. Autonomic dysfunction is one of the proposed mechanisms for nocturnal enuresis in children. The objective of current study was to evaluate autonomic nervous system functions in enuretic children. Twenty-four-hour ambulatory electrocardiographic recordings were obtained, and the time domain variables of HRV were calculated. The results of the present study suggest that sympathetic nervous system hyperactivity is present in enuretic children. This may explain why some enuretic children do not respond to anticholinergic medications. If these conflicting results are confirmed by large-scale clinical studies, Holter ECG examinations may be used for rational approaches in treatment of nocturnal enuresis.