The 'in vitro' effect of flunoxaprofen on human polymorphonuclear leukocyte (PMN) activities has been studied. Preincubation of PMN for 30 minutes at 37\ub0C with flunoxaprofen inhibited their leucoattractant-induced migration in a dose-dependent fashion. The basal level of PMN oxidative metabolism, measured by chemiluminescence, was increased after preincubation with the drug; however, flunoxaprofen, in the same conditions, was able to inhibit the chemiluminescent response of zymosan-stimulated PMN. No significant effect on PMN phagocytic activity was found. These data indicate that the nonsteroidal anti-inflammatory drug flunoxaprofen may have direct effects on neutrophil migration and activation and suggest that the anti-inflammatory effects of the drug may be related, at least in part, to its direct action on neutrophil responses