BACKGROUND: Cigarette smoking increased the risk of acute cardiac events related with endothelial dysfunction and increased sympathetic activity. Impaired autonomic nervous activity is recognized as a considerable symptom of cardiac dysfunction and is strongly associated with increased risk overall mortality. METHODS: A total of 75 healthy habitual smokers (40 female, 35 male, mean age 36.5 +/- 8.5 years), and 73 non-smokers subjects (45 female, 28 male, mean age 34.6 +/- 7.2 years) were studied. LF and LF/HF ratio were significantly higher in smokers than in non-smokers. On the contrary, SDNN, SDANN, RMSSD, and HF values were lower in smokers compared to those in non-smokers. Not the duration of smoking but the number of cigarettes smoked per day was correlated with the HRV parameters and NT-pro BNP. Furthermore, the average levels of NT-pro BNP were found to be positively correlated with LF, LF/HF and inversely correlated with SDNN, SDANN, RMSSD and HF. RESULTS: As a result, smoking impaires sympathovagal balance and decreases the heart rate variability in healthy subjects. And even a one cigarette smoking leads to overt sympathetic excitation. Furthermore, smoking results in an increase in NT-proBNP levels and the changes in adrenergic nervous system and NT-proBNP levels are well correlated. CONCLUSION: These findings could contribute to the higher rate of cardiovascular events in smokers.