Background: Chronic heart failure (CHF) is a clinical syndrome with high morbidity and mortality and the full understanding and adequate treatment of this pathology remain a challenge. Nitric oxide (NO), a short half-life gas, plays an important role in the regulation of vascular homeostasis, influencing both endothelium and platelets. NO bioavailability depends not only on its synthesis but also its degradation, mediated by reactive oxygen species (ROS), mainly superoxide anion (O2.-). We have previously demonstrated that CHF patients with sinus rhythm have platelet hyperggregability associated with alterations in NO bioavailability and oxidative stress1. Objective: The aim of this study is to investigate the effect of physical training (PT) on the intraplatelet L-arginine-nitric oxide pathway, oxidative stress and inflammatory markers in CHF without arrhytmias. Methods: Thirty CHF patients with left ventricular ejection fraction (LVEF) of 31±1% were randomized to 24 weeks of supervised exercise training (consisting of 30 minutes of moderate intensity treadmill exercise followed by resistance and stretching exercises, performed three times a week) or to a control group that remained sedentary. Blood was drawn before and after the intervention for platelet and plasma obtainment. The Ethical Committee of the State University of Rio de Janeiro approved this work (CEP-1435), and informed consent was obtained from each of the patients. The student t test was used for statistical analysis and statistic difference was considered when p<0.05. Results: Exercise tolerance was significantly increased in CHF patients who were submitted to exercise training. Platelet aggregation induced by ADP and collagen was significantly reduced in CHF patients after 24 weeks of exercise training. Paradoxically, nitric oxide synthase activity in platelets, assessed by the conversion of L-[3H]-arginine into L-[3H]-citrulline, decreased after exercise training, and no significant difference was observed in intraplatelet cGMP levels among the groups. In relation to oxidative stress markers, systemic and intraplatelet TBARS production and carbonylation were diminished after 24 weeks of training in CHF patients. Moreover, systemic levels of CRP, fibrinogen and TNF-α were also reduced in CHF after training. Conclusion: Our results suggest that chronic exercise has anti-oxidant, anti-inflammatory and anti-aggregant effects, regardless of NO production, showing it be an important non-pharmacological tool in the treatment of CHF.