The ring opening polymerization of ε-caprolactone catalyzed by organic acids had been studied. The aim of this study was to develop and optimize a process for obtaining poly-ε-caprolactone of high purity intend- ed for use as a drug carrier, with consideration of the impct of the monomer-catalyst ratio on the product parameters, the temperature impact and the impact of the type of catalyst on the product properties. The studies also aim to determine the possible positive effect of microwave radiation on the course of the reaction. The structures of the synthesized compounds were proven by 'H NMR spectroscopy. The average molecular weight of the obtained polymer particles was estimated based on the relations of the 'H NMR signal integrations. In the reaction catalyzed by citric acid the product was characterized by a substantially higher molecular weight compared to the analogous reaction using another type of catalysts. Higher average molecular weights were obtained by conducting the reactions under microwave radiation.