Abstract: The effects of salinity and body weight on oxygen consumption of Taiwan red tilapia (Oreochromis niloticus×O. mossambicus) were studied. The fish was divided into three groups by their body weight: 1.57～4.87 g (G₁),7.07～18.23 g (G₂) and 31.50～52.41 g (G₃). The results showed that oxygen consumption at diffe-rent salinities was significantly different (P<0.01). The rates of oxygen consumption in G₁ and G₂ were highest,with 0.41 mg O₂·g^-1·h^-1 for G₁,and 0.34 mg O₂·g^-1·h^-1 for G₂ respectively at salinity 7‰; while G₃ had highest level with 0.30 mg O₂·g^-1·h^-1 at 35‰. The lowest oxygen consumption level appeared at diffe-rent salinities with the different body weight. The lowest level in G₁,0.27 mg O₂·g^-1·h^-1,appeared at salinity 14‰. G₂ and G₃ had lowest oxygen consumption level at 21‰,with 0.22 mg O₂·g^-1·h^-1 and 0.13 mg O₂·g^-1·h^-1 respectively. ANOVshowed that oxygen consumption was significantly affected by the interaction of salinity and body weight.