Co1-x(Ta,Zr)x (0.05leq x leq 0.16) amorphous films with zero magnetostriction have been deposited by rf sputtering and their magnetic properties and thermal stabilities have been investigated. The amorphous films with zero magnetostriction are obtained in the composition range of Co content as high as 95 at.%. Saturation magnetization 4&piMs at room temperature of 95 at.% and 85 at.% Co-Ta-Zr films is about 15 kG and 10 kG, respectively and varies in proportion to the Co content in the films. These amorphous films have low coercive force Hc of about 0.1 Oe. Crystallization temperature Txof these films decreases monotonically with an increase of Co content and the films with a Co content of 93 at.% have Txof about 460 °C. Hc of these films with Co content less than 92.4 at.% changes little by annealing at a temperature below 350 °C. However, large uniaxial magnetic anisotropy is induced in the films by the annealing in a static magnetic field at a temperature above 300°C and these Co-Ta-Zr amorphous films have large unstable induced magnetic anisotropy.