Calcium phosphates (CaP) attract attention due to their role in the normal and pathological mineralization, as well as in industrial processes. Calcium hydrogenphosphate dihydrate (DCPD) is one of the major calcium phosphates minerals which can be found in kidney stones, dental caries and used in the industrial processes. Because of its crystal structure and morphology, DCPD represents a good model system for studying amino acids and crystals interactions in purpose of understanding mineralization process. In the biological mineralization, inorganic salts are formed in the contact with organic matrix, which is mostly composed of proteins. Although the basic principles of protein and crystal interaction are known, the role of certain amino acids is still not clarified. Clarification of their role would allow the preparation of additives to obtain minerals of desired properties. Amino acids are the basic building blocks of proteins. A common feature of all amino acids is the presence of at least one amino group and one carboxyl group. The side chain of the amino acids, designated by R, is different for each of the amino acid and it determinates its structure. The aim of this research was to synthesize DCPD seed crystals and investigate the transformation of seed crystals in metastable solution in conditions similar to physiological ones (pH 7,4, temperature 25 °C), in the presence of aspartic acid, asparagine and polyaspartic acid. DCPD was prepared by rapid mixing of equal volumes of calcium hydroxide and phosphoric acid solutions. Systems were magneticaly stireed for 1 hour at (25 ± 0.1) °C. Crystal growth and transformation of DCPD seed crystals in metastable solution (c(CaCl2) = c(Na2HPO4) = 4,2 mmol dm^-3, c(NaCl) = 0,15 mol dm-^3, pH 7,4) in the presence of different concentrations of aminoacids were followed potentiometrically. Precipitates were taken after different times determined on pH curves and characterized by IR spectroscopy, X-ray diffraction and scanning electron microscopy. Obtained results have shown that the synthesized seed crystals occur in the form of big plate-like crystals typical for DCPD. In all precipitation systems after 4 or 5 hours, calcium defitient hydroxyapatite (CaDHA) precipitates. Aminoacids don't have an effect on structure and morphology of the precipitate, but they do have an influence on the rate of transformation, depending on concentration present in the system.