A tranquillo-sedative substituted 1,3,4,5-tetrahydro-2H-1,4-benzodiazepine-2-one of the formula (I), ##STR1## wherein R.sub.1 is halogen or nitro, R.sub.2 is hydrogen or methyl, R.sub.3 is --CONH.sub.2 or --CONHCH.sub.3, and R.sub.6 is phenyl or halophenyl.