Abstract A method has been developed for the rapid quantitative analysis of chloroquine and its metabolite desethyl-chloroquine in plasma, blood and urine using high-performance liquid chromatography. An ethylene dichloride extract of the alkalinized biological samples was extracted with dilute acid and chromatographed on a reversed-phase column. Phosphate buffer in acetonitrile was used as the mobile phase with perchlorate as the counter-ion. Ultraviolet absorption at 254 or 340 nm or fluorescence detection was used. The fluorescence spectra and the fluorescence quantum yield of the substances were determined. Chloroquine and desethyl-chloroquine concentrations in the range of 10 nmol/l (UV-detection) and of 0.5 nmol/l (fluorescence detection) could be accurately measured with a relative standard deviation of 12%. The method should be adequate for therapeutic and pharmacokinetic studies.