This study evaluated whether the reduction of the neutrophil oxidative burst by N-acetylcysteine improves pulmonary gas exchange during a six minute maximal ergometer row. Healthy trained oarsmen were double-blinded randomized to either N-acetylcysteine (6 g daily for three days) or placebo groups. As determined by the relative changes of the zymosan-stimulated luminol-enhanced chemiluminescence response, N-acetylcysteine suppressed the exercise-induced enhanced neutrophil oxidative burst response to rowing (-7 ± 6 % vs. 17 ± 8 %; P < 0.05). This was the case although the concentration of neutrophils remained similarly elevated above the pre-exercise level in both trials (to 5.4 ± 0.5 vs. 5.9 ± 0.6 × 109 cells × l-1, respectively, P > 0.05). In the placebo and N-acetylcysteine groups, pulmonary ventilation increased and the arterial CO2 partial pressure decreased to the same extent during exercise. Also, at the end of exercise the arterial O2 partial pressure (77 ± 1 vs. 78 ± 1 mmHg), haemoglobin O2 saturation (92 ± 1 % vs. 93 ± 1 %) and O2 uptake (5.0 ± 0.2 vs. 4.9 ± 0.2 I × min-1) were not significantly affected by N-acetylcysteine. Equally, two hours after exercise, the pulmonary diffusion capacity was reduced by 7 ± 2 % below the pre-exercise with no significant influence of N-acetylcysteine. We conclude that the neutrophil oxidative burst to exercise does not influence pulmonary gas exchange during and after maximal rowing.