A liquid chromatographic method with UV detection for simultaneous determination of cefepime, vancomycin and imipenem has been developed. Cefuroxime was used as internal standard. After the clean up of samples by plasma protein precipitation, 5 microl of the extract were injected into the chromatograph and peaks were eluted from the Sulpelcosil LC-18 column using a mobile phase consisting of 0.075 M acetate buffer:acetonitrile (92:8, v/v), pH 5.0 at low rate (0.8 ml/min). The detection wavelength was 230 nm. The limit of detection was 0.4 microg/ml for cefepime and 0.2 microg/ml for vancomycin and imipenem. The method was applied to plasma samples of burn patients, and only small volumes of plasma were required for the simultaneous determination of those antimicrobial agents.