In this study, the effects of meloxicam, a not steroidal anti-inflammatory drug (NSAID), on the oxidative status were evaluated in exercised horses. Sixteen healthy horses were normally trained for 2 hours and immediately after, the half of them were intravenously injected by a single dose of meloxicam (0.6 mg/kg) whereas the 8 others were treated with NaCl 0.9% in the same way. Physical parameters (rectal temperature, heart and respiratory frequencies) and eventual inflammatory clinical signs, venous blood gas, serum biochemical markers such as glucose and protein concentrations, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities and plasma malondialdehyde (MDA) concentrations and superoxide dismutase (SOD) activities were investigated before (-2 hours), immediately after the exercise and 1, 3, 5 and 7 hours after. Immediately after the exercise which has induced a transient CO(2) accumulation coupled to a high and prolonged O(2) consumption, the physical parameters, the serum AST activities and the plasma MDA concentrations significantly increased whereas the plasma SOD activities were greatly reduced. Compared to the control horses, the meloxicam treated horses exhibited a more rapid clinical recovery associated to a more efficient CO(2) elimination and tissue O(2) delivery, less prolonged AST variations and marked increases in the SOD activities in the post-exercise period. These results demonstrate that a strenuous exercise induced an oxidative stress in horses and that meloxicam affects the oxidative status by strengthening the SOD activity.