A validated rapid and sensitive capillary zone electrophoretic method for the determination of olopatadine hydrochloride (OLO) is described. Optimum conditions were found: 20 mmol/L sodium tetraborate buffer, acetonitrile 15% (v/v), 10 mmol/L NaCl at pH 9.5, with 25 kV of applied potential, injection time of 10 s at 5x10(3) N/m(2), at a wavelength of 205 nm, and fixed temperature of 30 degrees C. The calibration curve was linear in the range of 1.13 x 10(-5) mol/L (4.22 mu g/mL) to 5.65 x 10(-5) mol/L (21.12 mu g/mL), with R=0.9995 for interday precision. LOD and LOQ values were 1.58 x 10(-6) (0.58 mu g/mL) and 4.78 x 10(-6) mol/L (1.75 mu g/mL), respectively. Precision values were 1.10-1.97% for intraday and 1.41% for interday RSDs. Accuracy was tested by preparing a synthetic mixture whose composition was similar to the pharmaceutical preparation for Patanol. The RSDs of the recovery values (98.2%) were between 0.42 and 0.65% and the amount of OLO found was 1.09 mg/mL. The result was within the requirements of USP 31-NF 26. Therefore, this validated method is suggested for routine analysis for the determination of OLO in laboratories.