Pharmacokinetics of drugs in the human interstitial space fluid can be monitored by means of microdialysis. However, the small-volume microdialysis samples containing low drug concentrations require a sensitive analytical method. In the present study, micellar electrokinetic chromatography (MEKC) is described for the quantification of cefpirome in human microdialysis and plasma samples. Sample preparation of human plasma samples by ultracentrifugation was suitable for comparison of plasma and microdialysate concentrations. Limits of quantification were 2 mu g/mL and 0.3 mu g/mL for plasma and microdialysate samples, respectively. The limit of detection (LOD) was estimated at 0.2 mu g/mL for the plasma and microdialysate samples. in conclusion, MEKC is a reliable and reproducible technique for measuring cefpirome concentrations in microdialysates as well as centrifuged plasma samples.