A novel method for the fabrication of acetylene black-dihexadecyl hydrogen phosphate (AB-DHP) composite film modified glassy carbon electrodes (GCEs) was presented, and based on this, a sensitive electrochemical method for the determination of hydroxycamptothecin (HCPT) was developed. Compared with the poor signal at GCE, the electrochemical response of HCPT at AB-DHP composite film modified GCE was greatly improved, which was confirmed by the significant enhancement of the oxidation Current. After the optimization of experimental parameters, the dependence of oxidation current on HCPT concentration was explored, which exhibited a good linear relationship in the range of 1.0 x 10(-9) to 1.5 x 10(-6) mol l(-1). The detection limit of HCPT was also examined and a low value of 5.0 x 10(-10) mol l(-1) for 6 min accumulation was obtained (S/N = 3). This electrode was Successfully applied to the detection of HCPT in cancer patient's serum samples. (c) 2004 Elsevier B.V. All rights reserved.