A new chemically modified electrode based on the immobilization of Pt particles is fabricated and exhibits electrocatalytic oxidation for L-cysteine (L-Cys), glutathione (GSH) and penicillamine (PEN) with relatively high sensitivity. It is also adaptable to HPLC for pulsed amperometric detection (PAD) of these thiols. PAD largely improves the detection sensitivity because the alternated polarizations can effectively clean and reactivate the electrode surface. It is shown that the peak currents of L-Cys, GSH and PEN are linear to their concentrations, with the calculated detection limit of 1.1 x 10(-7), 1.8 x 10(-7) and 3.8 x 10(-7) mol L(-1), respectively (S/N = 3). The method has been successfully applied to assess the contents of L-Cys and GSH in rat striatal microdialysates. The average contents of the two analytes in rat striatum are 2.6 x 10(-6) and 2.8 x 10(-6) mol L(-1), respectively.