Abstract: Biologically active solid systems are disclosed, containing immobilized organic compounds, such as medicines, in the form of materials appropriate as bone fillers, implant coatings or other alike systems, of the common formula B—P-A, where B is an inorganic support consisting of calcium phosphate, calcium hydroxyphosphate (hydroxyapatite), their mixture, or some other biocompatible mixture containing these or other insoluble inorganic phosphates, —P— is a phosphoryl group —P—O—, and A is the residue of the immobilized, organic, biologically active compound, such as a medicine, containing unprotonated amine and/or hydroxide group(s), and a method of their preparation consisting of the treatment of inorganic phosphate with a grafting reagent and consequent reaction with organic compound. As a grafting reagent, phosphorus pentachloride is applied and all operations are completed in an aprotic solvent.