The study was attempted to scrutinize the normal osmotic fragility of erythrocytes in domestic poultry such as chicken, quail and duck making a comparison with that in domestic mammalia such as dog and pig. Osmotic fragility of erythrocytes was determined on blood samples from 10 healthy adult animal in each species. Optical initial hemolysis of erytyrocytes occurred at $0.395{pm}0.03%$ Nacl for chicken, $0.410{pm}0.03%$ for duck, $0.440{pm}0.02%$ for quail, $0.470{pm}0.05%$ for dog and $0.560{pm}0.03%$ for pig. Optical complete hemolysis of erytyrocytes occurred at $0.270{pm}0.02%$ Nacl for chicken, $305{pm0}.03%$ for duck, $0.360{pm}0.02%$ for quail, $0.370{pm}0.03%$ for dog and $0.455{pm}0.03%$ for p. In other words, erythrocytes of poultry have stronger resistance to osmotic Iysis than that of mammalia, showing the strongest resistance In chicken among the tested poultry.