The fluorescent diastereoisomeric adducts formed in a precolumn derivatization reaction of enantiomeric alpha-substituted amino acids with o-phthalaldehyde and N-acetyl-L-cysteine were separated by high-performance liquid chromatography on a conventional reversed-phase column. This method was particularly efficient for the complete analytical resolution of alpha-substituted glutamic acid analogues, such as 2-methylglutamic acid, and several cyclic analogues (1-amino-1,3-dicarboxycyclohexane, 1-amino-1,3-dicarboxy-2-cyclohexene and 1-amino-1,3-dicarboxycyclopentane). The order of elution from the column was correlated with the absolute configuration of the derivatives.