The amperometric detection (AD) employing a carbon disk electrode as a working electrode to determine the thiol compounds, including cysteine (CYS), glutathione (GSH), 6-thiopurine (TP), and methimazole (MMI), following their separation by capillary zone electrophoresis (CZE) is described in this paper. The detection potential was chosen at +1100 mV and all analytes exhibit good response at this potential on the carbon disk electrode. The reproducibility, linearity, and recovery were evaluated under the optimum conditions. The four analytes can be baseline resolved within 20 min and the detection limits reached about 10(-6) mol/l of magnitude. The method was applied to the separation and determination of the actual thiol samples and the analytical results were satisfactory.