A method was developed and validated for the simultaneous analysis of (+)- and (-)-bevantolol in human plasma. The assay involves plasma protein precipitation, derivatization of racemic bevantolol to its diastereomeric thioureas with 2,3,4,5-tetra-o-acetyl-alpha-D-glucopyranosyl isothiocyanate, and solid-phase extraction of the diastereomers from 0.5 ml human plasma. Chromatographic separation was accomplished under isocratic conditions using a reversed-phase C-18 analytical column and mobile phase consisting of equal parts of 75 mM dibasic ammonium phosphate buffer (adjusted to pH 3.5 with phosphoric acid) and acetonitrile, with a detection wavelength of 220 nm. The absolute peak-height method was employed for quantitation. Retention times for the diastereomers of (+)- and (-)-bevantolol were 7.4 and 6.4 min, respectively. The method is suitable for the quantification of the enantiomers over a concentration range of 40 to 800 ng/ml per enantiomer.