Calcium deficient apatites, which could be used as precursors of the inorganic component of biological apatites, have been synthesised by controlled crystallisation. The influence of the pH and the reaction time in the calcium deficiency and the crystal size of samples have been studied. For determination of Ca/P ratio of as-received apatites, a method based on Rietveld profile analysis of X-ray diffraction data is proposed. The results obtained using this method agree well with those obtained by other classical analytical methods.