In this study, the lethality as well as the biochemical and histological effects of Cobra (Naja haje) envenomation at a sublethal dose has been investigated in mice and rats.          The venom injected intraperitoneally in rats (0.2 mg/kg) produced marked increase in the activities of ALT, AST, ALP and LDH. Also, serum glucose, urea and creatinine levels were significantly elevated. These results are in accordance with the histological findings of the liver that showed vacuolated hepatocytes and scattered necrotic and haemorrhagic areas together with congestion and dilatation of blood vessels and sinusoids. The spleen also displayed small diffuse white pulps with ill-defined outlines and extravasation of blood that extended to infiltrate the widened sinusoids. The venom also produced severe degeneration of the cardiac muscle with loss of striations and extensive haemorrhage inbetween the myocardial bundles.          These biochemical and histological envenomation disorders, were markedly and effectively neutralized by the polyantivenins (non-irradiated and gamma-irradiated in a sterilizing dose of 25 kGy). The neutralization ability of both antivenins was the same against a lethal dose of the venom (2.5 LD50). The minimal protective dose of the polyantivenins was calculated to be 16000 µg/20 gm mouse. Rats injected with mixtures of venom and antivenins (non-irradiated and irradiated) showed a decrease in all elevated biochemical parameters investigated. The histological examination also showed less severe injuries in all organs examined (liver, spleen and heart) which appeared more or less normal with very few abnormalities remaining.          Comparative study was also done on these antivenins using immunodiffusion technique which showed the same precipitin bands with the tested venom. Thus, it can be concluded that both antivenins (non irradiated and 25 KGy gamma-irradiated) have similar immunoglobulins and have no differences in their antilethal and enzymatic neutralizing ability as well as in ameliorating the degree of tissue damage induced by the venom.