Introduction of a methyl moiety to the C9 position of a 1,4-benzodiazepine ring system afforded dual CCK-A and -B antagonistic activity. Novel derivatives having ethyl, isopropyl and chloro substituents at C9 were prepared in order to obtain more potent antagonistic activities. AM1(MOPAC93) calculations of the dihedral angles between the N1 and C9 substituents indicated that dihedral angles for dual antagonistic activities were between 50 degrees and 60 degrees. A methyl moiety was selected as the most suitable C9 substituent in this series for potent dual CCK-A and -B receptor antagonistic properties.