When making prescriptions for total parenteral nutrition (TPN) it is necessary to take into consideration also substitution with calcium and phosphorus. Under some clinical conditions, or in certain groups of patients, it is necessary to supply these substances in high doses with a reduced volume, which due to mutual interactions may be problematic. This experimental paper therefore examined the compatibility of commercially available or individual preparations containing the compounds of calcium and phosphorus. These preparations were examined in a mixture with clinically employed solutions of amino acids or with solutions of glucose. The evaluation was performed by titration until the development of a visible precipitate and also by means of the pharmacopoeial method of evaluation of particles below the level of visibility. Hydrogen phosphate was found to possess a lower compatibility and stability in mixtures containing calcium salts in comparison with dihydrogen phosphate or organic phosphate. Nevertheless, no significant differences were found between dihydrogen phosphate and organic phosphate. The experiment confirmed a better stability of organic calcium salt versus the inorganic one only in the samples containing solutions of amino acids. Of the solutions of amino acids under study, the best stabilizing properties were found in the solutions intended for use in neonatology and paediatrics.