Novel 2-amino-6-biphenylacetic acids, esters, and metal salts are provided of the formula
wherein R represents a hydrogen atom or a lower alkyl group or sodium or potassium atom, R1 represents a fluorine, chlorine or bromine atom or a lower-alkyl or amino group; R2 represents a lower-alkyl, lower alkoxy, amino or trifluoromethyl group or a fluorine, chlorine or bromine atom; n is 0-3 and m is 0-2, or the pharmaceutically acceptable salts thereof or hydrates thereof. The compounds exhibit muscle relaxant activity, and are also useful as anti-inflammatory agents.