The structural and magnetic properties of Gd3(Fe1-xCox)25Cr4 compounds with x = 0-0.6 have been investigated. The structures of all the compounds investigated are found to possess monoclinic symmetry and belong to the A2/m space group. Substitution of Co for Fe leads to a clear contraction of the unit-cell volume. The Curie temperature increases from 492 K for x = 0 to 762 K for x = 0.6. The composition dependence of the saturation magnetization at 5 K reaches a maximum around x = 0.3. It is noteworthy that substitution of Co for Fe results in a significant change of the magnetocrystalline anisotropy of the Co sublattice, and changes the easy magnetization direction of Gd3(Fe1-xCox)25Cr4 compounds from basal plane to easy axis. © 1999 American Institute of Physics.