The paper aims to study the possibilities of determining vancomycin in the serum by the method of capillary isotachophoresis. The leading electrolyte contained Na+ as the leading ion, morpholinoethanesulphonic acid as the counter-ion (pH 6,2), and methylhydroxyethyl cellulose as the additive. The terminating electrolyte was morpholinoethanesulphonic acid. The conductivity detector was employed for detection. Ethanol was selected for precipitation of proteins. The yield of vancomycin from the serum was 89-91%. The calibration curve is linear in an interval of 0.02-0.5 microgram (the absolutely dosed amount). The limit of vancomycin determination in the serum is 4 micrograms/ml. The method was employed to determine vancomycin in the serum of patients. The obtained results correlated well with those obtained by fluorescent polarizing immunoanalysis (TDx) in a concentration interval of 4-30 micrograms/ml.