A stereoselective RP-high performance liquid chromatography (HPLC) assay to determine simultaneously the enantiomers of esmolol and its acid metabolite in human plasma was developed. The method involved a solid-phase extraction and a reversed-phase chromatographic separation with UV detection (λ=224nm) after chiral derivatization. 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (GITC) was employed as a pre-column chiral derivatization reagent. The assay was linear from 0.09 to 8.0μg/ml for each enantiomer of esmolol and 0.07-8.0μg/ml for each enantiomer of the acid metabolite. The absolute recoveries for all enantiomers were>73%. The intra-and inter-day variations were<15%. The validated method was applied to quantify the enantiomers of esmolol and its metabolite in human plasma for hydrolysis studies.