Calcium phosphates (CaP) have an important role in biological and pathological mineralization and industrial processes. One of the biologically most important calcium phosphates is octacalcium phosphate (OCP), one of the components of dental and kidney stones. Because of its crystalline structure and morphology, OCP represents a suitable model system for studying the crystal – additive interactions with the aim to contribute to the understanding of biomineralization 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 specific amino acids is still not clarified. Clarification of the role of individual amino acids would allow the preparation of tailored additives enabiling to obtain the minerals of desired properties. The aim of this research was to synthesize OCP seed crystals and investigate their transformation in conditions similar to the physiological (pH 7.4, temperature 25 °C), in the presence of aspartic acid, asparagine, polyaspartic acid and lysine The OCP seed, was prepared by a modified method according to Boanini by dropwise adding of calcium acetate solution (c = 0.04 mol dm^-3) in phosphate solution (c(Na2HPO4) = c(NaH2PO4·H2O) = 5 mmol dm^-3) for 2 hours at 70 °C with mechanical stirring. Crystal growth and transformation of OCP 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 based on pH curves and characterized by FTIR spectroscopy, scanning electron microscopy and powder X-ray diffraction. Obtained results have shown that the OCP seed crystals precipitate in the form of typical, big needle-shaped plate-like crystals. Amino acids affect the rate of OCP transformation, depending on the concentration in which they are present. Asparagine and lysine do not affect the composition and morphology of the precipitate. As in the control system after 4 hours, the OCP transformation in CaDHA is almost complete. Rendogenograms of powders formed after 4 hours in the presence of asparagine and polyaspartic acid indicate a possible beginning of further transformation of CaDHA.