The importance of arterial and venouse blood gas in the diagnosis of experimentally induced respiratory tract diseases in lambs and to the most reliable which parameters in the diagnosis of disaese were aimed to determine in this study The lambs divided to control ( 6 lambs) and experimental ( 7 lambs) groups. Pasteurella haemolytica (8x10⁸ CFU/ ml), Clebsiella pneumoniae (8x10⁸ CFU/ml) and Paraenfluenza 3 viruse were inoculated by intratracheal for induced respiratory tract diseases in the lambs (experimental groups). Blood samples were taken from the femoral arteria and the jugular vein once in the control group of lambs. Blood samples were taken Irom the femoral arteria and the jugular vein on days 1th , 2th. 3th, and 4th of the infection in the experimental group of lambs The WBC (p<0.00l), body temperature (p<0 001), respiratory rate (p<0.001), and heart rate (p<0.01) were significantly increased in the experimental group of lambs compared with the control group of iambs. pH (p<0.01), pCO2 (p<0.01), pO2 (p<0 05). and oxygen saturation (p<0.05) in venouse blood were significantly different in the the experimental group of lambs compared with the control group of lambs. pCO2 (p<0.01) In arterial blood was significantly different in the the experimental group of lambs compared with the control group of lambs. In the histopathologic examination, interstitial pneumonia and pneumonia with ab-cessation was determined in the lung of experimental group of the lambs. The results ot this study showed that, arterial blood gases did not influenced in acute respiratory enfection, but venouse blood gases did more influenced in acute respiratory disease, therefore, evaulation of venouse blood gases in the diagnosis of respiratory disease was found to more benifical.