The simultaneous analysis of 14 diuretics in human urine (belonging to five different pharmacological groups) by reversed-phase high-performance liquid chromatography (HPLC) with a diode-array detector was developed by using a gradient elution with acetonitrile and phosphate buffer containing propylamine hydrochloride on a Bondclone-ODS (10 microns) column. The method was applied to the screening test of several diuretics abused by athletes. The confirmation analysis was performed by gas chromatography-mass spectrometry with ion-selective detection (GC-MSD). The characteristic mass fragment ions obtained by electron-impact (EI) ionization (70 eV) provided sufficient identification of these diuretic agents. During the 1990 weight-lifting contest of Asia in Kao-Hsiung, Republic of China, one urine sample was found positive for the diuretic hydrochlorothiazide.