A stereoselective CE assay for the determination of the enantiomeric purity of (R)-(-)chloroquine and (S)-(+)-chloroquine was developed and validated. The separations were performed in a 50.2/40 cm uncoated fused silica capillary at 20 degrees C using a 100 mM sodium phosphate buffer, pH 2.5, containing 30 mg/mL sulfobutylether(VII)-beta-cyclodextrin as background electrolyte operated at an applied voltage of -25 kV and 20 degrees C. The detection wavelength was 225 nm. Carbamazepine was used as internal standard. The assay was validated in the range of 0.05-1.0% for the respective minor chloroquine enantiomer based on a concentration of 3 mg/mL of the major enantiomer, either (R)-(-)-chloroquine or (S)-(+)-chloroquine. The method was applied to analyze the stereoisomeric purity of synthetic samples of the chloroquine enantiomers.