The oxygen diffusion coefficients in isolated skeletal muscle fibres of Baikal seal and grayling, white rat, chicken were calculated on the basis of experimentally determined curve of dependence of the O2 consumption on pO2 and the radius of the fibres. In all the cases, the diffusion coefficient was smaller in the fibres than in water. The oxygen diffusion coefficient was increased during embryogenesis and postnatal period in chicken. The influence of different parameters of the oxygen transport and of properties of different fibres on the values of the oxygen diffusion coefficients, are discussed.