Abstract: Objective To study the impact of 24-hour sleep deprivation（SD） on arrhythmia and heart rate variability（HRV） in normal individuals. Methods Alterations of dynamic electrocardiogram and serum hydrocortisone in 30 healthy volunteers were observed before and 24h after SD. Results Twenty-four hours after SD,the high frequency（HF） of HRV was significantly reduced（P＜0.05）,while the low frequency（LF） of HRV,the LF/HF,and the serum hydrocortisone level were significantly increased（P＜0.05）.The atrial and ventricular premature beats were observed in certain patients. Conclusion Atrial and ventricular premature beats,elevated hydrocortisone level,arrhythmia and HRV,in normal individuals 24h after SD,may be related with a lower vagal activity and an elevated sympathetic activity.