The therapeutic effect of 1 mg/kg of dexamethasone on lung oedema and respiratory distress induced by 0.08 mg/kg of oleic acid (OA) in dogs was investigated into 8 dogs. One hour after OA injection, blood pH, HCO3, PO2, O(2)Hb, and heart rate decreased, whereas COHb, PCO2, temperature, and respiration rate increased. Lung oedema was confirmed histopathologically in a dog from the control group who died. Blood pH, COHb, temperature, and respiration rate returned to normal values after administration of dexamethasone. It has been determined that respiratory distress and lung oedema cause important changes in blood gases and the administration of a single dose of I mg/kg of dexamethasone is effective in the treatment of lung oedema and respiratory distress induced in dogs by OA.