Abstract: The invention relates to new optically active or racemic 5-phenyl-1,3,4,5-tetrahydro-2H-1,4-benzodiazepin-2-one derivatives of the general formula (I) ##STR1## wherein R.sup.1 stands for hydrogen, halogen, trifluoromethyl or a nitro group;R.sup.2 stands for hydrogen or alkyl having 1 to 6 carbon atoms;R.sup.3 represents a group conventionally attached to the --CH(NH.sub.2)--COOH group of the known optically active or racemic .alpha.-amino-acids, preferably an optionally substituted lower alkyl group;R.sup.4 is hydrogen, chlorocarbonyl or carbamoyl; andX is hydrogen, halogen or trifluoromethyl, with the proviso that if in the racemic compounds R.sup.4 stands for hydrogen R.sup.3 is other than alkyl having 1 to 6 carbon atoms, in which the centers of asymmetry in the 3- and 5-positions have the same absolute configuration, and pharmaceutically acceptable acid addition salts thereof, and a process for their preparation.