Structure and magnetic properties of ferrimagnetic bioceramics in the system {0.45(CaO, P2O5) ySiO(2) xFe(2)O(3) 0.03Na(2)O}, x=0.05, 0.10, 0.15, 0.20, were studied by x-ray powder diffraction and magnetic measurements. Magnetite and calcium phosphate, crystallizing in the hexagonal and monoclinic crystal systems, are the major phases in the compounds. Phase development, crystal structure, and magnetic properties of the composites are determined by the specific starting composition of oxides and the heat-treatment temperature.