A direct, isocratic, sensitive and precise liquid chromatographic method is presented for the enantiomeric separation of aminoglutethimide (AG) and its acetylated metabolite (AcAG) using cellulose tris-3,5-dimethyl phenyl carbamate (Chiralcel OD) and cellulose tris(4-methylphenyl benzoate) ester (Chiralcel OJ) columns in series. The enantiomeric elution order is determined by separate chromatography of the racemate AG and racemate AcAG and of their separate enantiomers under similar conditions. This method has been used to determine and identify the enantiomers of AG and AcAG in the urine sample collected from a metastatic breast cancer patient after administration of AG for 24 h. Large amounts of (+)-R-AG are excreted unchanged in the urine together with smaller quantities of (+)-R-AcAG, while most of the (-)-S-AG is metabolically converted into (-)-S-AcAG.