BACKGROUND: Cigarette smoking has been shown to adversely affect heart rate variability (HRV), suggesting dysregulation of cardiac autonomic function. Conversely, smoking cessation is posited to improve cardiac regulation. PURPOSE: The aim of the present study was to examine the effects of smoking cessation on HRV among a community sample of chronic smokers. METHODS: Sixty-two healthy male smokers enrolled in an 8-week smoking cessation program involving a nicotine transdermal patch treatment. Participants were assessed at baseline (while smoking regularly), at mid-treatment (while using a high-dose patch), and at follow-up, 4 weeks after patch discontinuation. Both time-domain (standard deviation of normal-to-normal (NN) intervals (SDNN), square root of the mean squared difference of successive NN intervals (RMSSD), and percent of NN intervals for which successive heartbeat intervals differed by at least 50 ms (pNN50)) and frequency-domain (low frequency (LF), high frequency (HF), LF/HF ratio) parameters of HRV were assessed at each visit. RESULTS: Successful quitters (n = 20), compared to those who relapsed (n = 42), displayed significantly higher SDNN, RMSSD, pNN50, LF, and HF at follow-up, when both nicotine and smoke free. CONCLUSIONS: Smoking cessation significantly enhances HRV in chronic male smokers, indicating improved autonomic modulation of the heart. Results suggest that these findings may be primarily attributable to nicotine discontinuation rather than tobacco smoke discontinuation alone.