A simple and fast method for the determination of urinary creatinine by high-performance capillary electrophoresis (HPCE) has been developed. The urine samples were diluted 50 fold before they were injected onto an HPCE column for analysis. with this technique, the urinary creatinine level can be determined within 4 min. The interference from urea in urine has been totally eliminated. The reproducibility and recovery of the technique have been studied and it was proven that the technique is satisfactory for quantitative determination of urine creatinine. The results obtained from this technique have been compared with results obtained by high-performance liquid chromatography, and the results from both techniques agreed quite well (correlation coefficient = 0.993). The linear range of the technique was over two orders of magnitude (0.1-11 mg/dl) which covers the creatinine concentration in human urine after 50 fold dilution. The detection limit for creatinine is 0.04 mg/dl with a signal-to-noise ratio of 3.