Using enantioselective gas chromatography (GC) with an octakis-(2,6-di-O-tert-butyldimethylsily~)-~cyc~~extrin column, the direct enantioselective analysis of 3-butylphthalide enantiomers was achieved. Investigations relating to their sensory characteristics and odour thresholds were carried out via enantioselective gas chromatographylolfactometry. In order to elucidate stereochemical features, the lactone structure of racemie 3-butylphthalide was hydrolysed and the carboxy function protected as an isopropylester: the hydroxy function at C-3 was esterified with (R)-2-phenylpropionic acid. The resulting diastereomeric esters were separated and isolated by high performance liquid chromatography. Absolute configurations were derived from 'H-NMR studies according to the Helmchen model, subsequently followed by ester cleavage and recylisation to the corresponding 3-butylphthalide enantiomers. Investigation of the essential oil of celery seed show enantiomeric distributions in the range of 95 : 5 in favour of the (3s)-enantiomer. This enantiomer shows a significantly lower GC odour threshold value than does the (3R)-enantiomer.