A method based on capillary electrophoresis with amperometric detection (CE-AD) has been developed for the simultaneous determination of 7-methylguanosine and mitomycin C. The detection electrode was a 0.3 mm carbon disc electrode at a working potential of 950 mV (versus Ag/AgCl electrode). A suitable electrolyte consists of 20 mmol/L phosphate buffer (pH 9.4), with the separation voltage of 18 kV, the injection time of 10 s, and the injection voltage of 18 kV. Under optimum conditions, the two analytes could be well separated within 10 min in a 60 cm length capillary. The current responses were linear over about two orders of magnitude (0.50 - 50 mg/L) with detection limits (S/N = 3) of 0. 050 and 0.025 mg/L for 7-methylguanosine and mitomycin C, respectively. The proposed method was successfully applied to determine the synthetic urine and serum samples. The recoveries were found in the range of 93.0% - 97.2%.