Objective: Nitric oxide (NO) is a gas which has vasodilator, antioxidant and metabolic regulator features. The positive effect of aerobic exercise is well known on the production of NO in healthy men. However, the effects of chronic anaerobic exercise on blood NO levels remain unclear. The aim of the present study was to investigate the effects of both chronic aerobic and anaerobic exercise on basal serum nitric oxide (BSNO) levels, and the relationships between BSNO and some aerobic and anaerobic performance parameters. Material and Methods: Three groups participated in the present study, each of them was composed of 11 healthy men with similar physical characteristics. The groups consisted of volleyball players as the anaerobic group (AnG), swimmers as the aerobic group (AeG) with long-term exercise background and volunteers who did not exercise regularly as the control group (CG). BSNO (as total nitrite) analysis was determined in fasting venous blood by using Griess method. Mean power and peak power as the criteria of anaerobic performance were determined by using Wingate test, and lactate minimum speed (LMS) was determined as the criterion of aerobic endurance with the LMS test based on lactate elimination. Finger tip lactate measurements were taken during certain segments of LMS test. Results: The BSNO value of the AeG was significantly higher compared to the CG (90.34 vs. 74.39 mu M), but it was not different from that of the AnG (80.02 mu M). No significant relationships were observed between the BSNO and LMS values in any group. The LMS value of the AeG was significantly greater than that in the CG (11.59 vs. 10.27 km/h). Peak power (13.11 vs. 9.84 w/kg) and mean power (8.55 vs. 7.36 w/kg) were significantly greater in the AnG compared to the AeG. A positive correlation was found between BSNO in the AeG and peak power (r=0.648, p=0.031) in the AeG. Conclusion: Based on the results of the present study, it is suggested that regular aerobic exercise may improve blood NO levels while anaerobic exercise does not; nevertheless, NO may play a role in both aerobic and anaerobic adaptations to exercise.