OBJECTIVE: To study the changes of autonomic nervous function in the young adult with asthma through the heart rate variability(HRV). METHODS: Two groups of young adults, 23 healthy volunteers and 69 asthmatic young adults were divided into three groups according to the severity of asthma. Twenty-four hours Holter monitored and heart rate variability analysed. RESULTS: The HF and pNN50 that showed the vagal tone in asthma subjects increased as compared with the normal group, while the LF and SDANN that mainly showed the sympathetic tone decreased(P < 0.01). These values were remarkable in the severe asthma group (P < 0.01). CONCLUSION: Even in mormal condition when patients are free of asthmatic attack, autonomic nervous function of asthmatics differ from that of normal young adults.