Hyperimmune sera administered intramuscularly (i/m) in 4 months oldNewzealand rabbits either simultaneously with the virus or before its injection by 24, 48 or 72 hours give 100% protection against infection with the viral haemorrhagic disease of rabbits while 60% protection was given in rabbits treated with hyperimmune sera 24 hours post infection. IM administration of the virus killed 80% of the inoculated rabbits within 2-5 days, rabbit that recover was severely emaciated. The virus was able to agglutinate the erythrocytes of human type 0, chickens, quails, pigeons, sheep, goats, buffaloes, cattle, donkeys and camels but not ducks, although the haemagglutination (HA) titers varied. The HA titers of various tissues of rabbits which had died of experimental infection were in the folowing order: liver> spleen> kidney> lung> trachea> brain> heart. At the end of experiment the highest haemagglutination inhibition antibody titer (HI) was detected in the only survived rabbit i/m injected with the virus but the lowest was reported in rabbits treated in rabbits treated with hyperimmune sera before infection. There was no detectable precipitating line between the virus and the specific antisera in immunodiffusion test.