Traditional studies performed in dogs using NSAIDs evaluate eicosanoids levels, cytokines and other factors associated to acute inflammation response. The present study is focused on the oxidative burst, which measures the production of reactive oxygen species of blood and synovial leukocytes of dogs. Therefore, the aim of this study was to compare the effect of different NSAIDs and a steroidal drug on the phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst of blood neutrophils and synovial mononuclear cells by flow cytometry technique. The synovial fluid from both stifles and blood from 6 healthy dogs were collected in heparinized tubes and 10⁶ cells were incubated with 2'7'diacetate-diclorofluorescein (DCFH-DA) and carprofen (100 µM), or ketoprofen (100 µM), or hydrocortisone (100 µM), or meloxicam (100 µM) or buffer phosphate solution (negative control) for 30 minutes at 37°C. The comparative analysis of oxidative burst after PMA stimulus showed that carprofen (720 ± 30; p< 0,001), ketoprofen (700 ± 20; p< 0,001), hydrocortisone (716 ± 50 p< 0,01) and meloxicam (1150 ± 20; p< 0,05) were efficacious in attenuating the production of free radical by blood neutrophils when compared to negative control (1562 ± 45). The synovial mononuclear cells showed the same behavior: carprofen (103 ± 8; p< 0,001), ketoprofen (173 ± 9; p< 0,001), meloxicam (268 ± 3 p<0,05) and negative control (290 ± 4). All NSAIDs used in this study showed some inhibitory effect on PMA-induced oxidative burst compared with hydrocortisone, however meloxicam would have a lower trend potency on the oxidative burst process.