A process for preparing industrially and efficiently glutamic acid compounds (such as monatin) useful as sweeteners or intermediates for the production of drugs or the like: a process for preparation of intermediates used therein: novel intermediates included among them: a process for preparation of optically active monatin: a process for preparation of intermediates used therein: and novel intermediates included among them. Specifically, a process for the preparation of glutamic acid compounds (or salts thereof) including monatin, which comprises preparing a ketoglutaric acid compound serving as a precursor of the objective glutamic acid compound by condensing a specific pyruvic acid compound with oxalacetic acid or pyruvic acid through cross-aldol reaction and, if necessary, subjecting the obtained condensate to decarboxylation, and replacing the carbonyl group of the ketoglutaric acid compound by an amino group.
