Two in vitro experiment were conducted for selection of the appropriate inhibitor of lipid peroxidation during storage of bull semen at 5*C up to 168 hours. In the first experiment, supplementation of citrate – or Tris – based diluents with 2.8 mg / ml pentoxifylline or 1.0 mg / ml EDTA or 2.0 mg / ml sodium thiosulfate or 0.1 mg / ml ascorbic acid or 1.0 mg / ml methionine or 0.005 mg / ml epinephrine or 2.0 mg / ml mannitol or 0.43 mg / ml sodium benzoate or 0.02 mg / ml 17 B – Estradiol resulted in a significant ( P< 0.01 ) improvement in sperm viability. The maximum values of sperm viability were achieved by sodium benzoate. Also, in the second experiment, 0.43 mg / ml sodium benzoate was capable of inhibiting ( P < 0.01 ) malonaldehyde production in stored semen and maintaining the functional competence of spermatozoa in terms of motility, acrosomal integrity and fertilizing ability.