Abstract A capillary zone electrophoretic (CZE) method was investigated for the determination of Gleevec and its main metabolite ( N-demethylated piperazine derivative) in human urine using a fused-silica capillary (75 μm I.D.×60 cm total length, 10 cm effective length). The separation was performed with an hydrodynamic injection time of 10 s (0.5 p.s.i.) a voltage of −25 kV, a capillary temperature of 25 °C and a 100 m M phosphoric acid adjusted to pH 2 with the addition of triethanolamine. Under these conditions, the analysis takes about 5 min. A linear response over the 0.4–30.0 mg l −1 concentration range was investigated for two compounds. A dilution of the sample was the only step necessary before the electrophoresis analysis. Detection limits of 0.1 mg l −1 for Gleevec and its metabolite ( S/ N=3) were obtained. The developed method is easy, rapid and sensitive and has been applied to determine Gleevec and its main metabolite in clinical urine samples.