OBJECTIVES The purpose of this study is to verify/partially validate pharmacopoeial HPLC methods for determination of impurities in drugs. The objective is to investigate the purity of tested substances and pharmaceutical product during the validation process and to provide an overview of the current guidelines and regulatory requirements for determination of impurities in drugs, with emphasis on HPLC methods. MATHERIAL/METHODS Research includes a review of available scientific literature in the field of analytics and quality control of medicines. The review includes scientific papers, the United States Pharmacopoeia (USP) and European Pharmacopoeia (Ph. Eur.), the latest editions of professional books, electronic sources and valid guidelines of regulatory bodies. The review of the regulatory guidelines was specifically directed towards ICH Harmonised Guidelines: (ICH): Q2 "Validation of Analytical Procedures: Text and Methodology", Q3A "Impurities in New Drug Substances", Q3B "Impurities in New Drug Products", Q6A "Specifications: Test Procedures and Acceptance Criteria for New Drug Substances and New Drug Products: Chemical Substances". Validation parameters which will be examined, as well as acceptance criteria which have to be met in order to successfully validate methods, are prescribed in method validation/verification protocols. All tests were conducted according to valid regulatory guidelines, including ICH Guidelines, Pharmacopoeias (Ph. Eur. and USP), in GMP environment. Tests were performed using appropriate HPLC instruments. Reference standards, as well as reagents of appropriate purity were used, in accordance with pharmacopoeias. RESULTS In the experimental part, the following validation parameters were tested during the verification of Ph. Eur. method for determination of related substances in nicotinamide: selectivity, precision, limit of quantification and stability of solutions. During the verification of USP method for limits of formaldehyde and acetaldehyde in polyethylene glycol 3350, the following parameters were tested: selectivity, precision, limit of quantification and stability of solutions. In the verification of Ph. Eur. method for determination of monomers: ethyl acrylate and methacrylic acid in the methacrylic acid – ethyl acrylate copolymer (1:1) and methacrylic acid - ethyl acrylate copolymer (1:1) dispersion 30 per cent, the following validation parameters were examined: selectivity, limit of quantification, precision and stability of solutions. During the partial validation of the analytical method for determination of related substances in the pharmaceutical product which contains active substance atenolol, the following parameters were checked: selectivity, linearity, limit of quantification, precision and accuracy. The results of all performed tests are within the acceptance criteria which were set for the validation parameters being examined. CONCLUSION Verification studies of pharmacopoeial methods for determination of impurities in pharmaceuticals, as well as a partial validation of HPLC method for determination of impurities in a pharmaceutical product have been successfully performed. The results of tests carried out will be used in the pharmaceutical industry and verified/validated analytical methods will be routinely applied in quality control of these products in quality control laboratories.