Mn-doped β-tricalcium phosphate was prepared by solid state reaction at 1100°C. The crystal structure of Ca 2.85 Mn 0.15 (PO 4 ) 2 , was determined by single crystal X-ray diffraction and found to be rhombohedral, R3c. Unit cell parameters are: a=10.3419(3); c=37.025(3)Å (hexagonal setting), Z=21. Structure refinement data show that from the five Ca positions the Ca(4) site is only half filled and that the Mn 2+ ions occupy the hexacoordinated Ca(5) site solely. EPR spectroscopy reveals that manganese in solid solutions Ca 3−x Mn x (PO 4 ) 2 (x=0.1; 0.28; 0.6) is divalent and supports the structure refinement results that Mn occupies the Ca(5) site with a geometry very near to a regular octahedron.