A method of determination of sulbaktam in human serum by capillary isotachophoresis with the use of a conductivity detector was worked out. Prior to the proper analysis, a pretreatment of the sample of serum was carried out by extracting sulbaktam to butyl acetate. The total yield of the proposed analytical procedure with an extraction first stage approaches 94%. The smallest determinable amount of the sample corresponds to 1 micrograms of sulbaktam in 1 ml of serum. The reported method was employed to evaluate the samples of sera of volunteers after intravenous administration of the dosage form sulbaktam-ampicillin (VUFB) and the foreign pharmaceutical preparation Unasyn (Pfizer). Statistically insignificant differences in pharmacokinetic parameters have confirmed that the preparations are highly bio-equivalent.