Abstract: Aim To study the protective effect of cobra venom factor (CVF), separated from the venom of Najanaja atra, on respiratory dist ress syndrome (RDS)induced by oleic acid.Methods The main parameters of respira to ry function in anaesthet ized dogs were co ntinually mo ni to red by mass spect rometer, pneumo-tachog raph and pressure transduce rs.The lung tissues were taken immediately after the experiment for histolo gical examination.Results CVF, given 20 h before the do sage depleting more than 95% of the complements, significantly at tenuated oleic acid-induced pulmonary dy sfunction.Histo logical examination showed improvement of hyaline membrane formation, alveolar haemo rrhag e and pulmonary arte riolar thrombosis.Conclusion Complement plays an important role in the development of lung injury induced by oleic acid.The depletion of serum complements by CVF inhibits the development of RDS

Key words: cobra venom factor, Najanaja atra, oleic acid, respiratory distress syndrome, complement