The novel 1,4-benzodiazepine-4-oxide aldehyde adducts of the invention are aldehyde adducts of benzodiazepines unsaturated at the 1 position, referred to as 3H-1,4-benzodiazepines. 3H-1,4-benzodiazepines are known, and are useful as sedatives and tranquillizers in the field of human therapy. The azeto-[1,4]-benzodiazepine ring structure is an entirely new heterocyclic ring structure.