Studies showed that tamoxifen treatment in horses with acute pulmonary inflammation promoted improvement in animals’ clinical status. We evaluated the effect of tamoxifen on equine peripheral blood neutrophils We did chemotaxis, respiratory burst and phagocytosis assays Tamoxifen has a direct action over neutrophilic functions (chemotaxis and respiratory burst) These results suggest that the effect of TX could explain the clinical improvement in horses with acute lung inflammation