Tricyclic benzodiazepine derivatives ("A") bearing a hydroxylower alkyl substituent in the 1-position and a heterocyclic ring joined between positions 4 and 5 of the benzodiazepine moiety are described. The heterocyclic ring will contain the nitrogen atom appearing at position 4 of the benzodiazepine ring as well as the hetero atom, which may be either oxygen or nitrogen, attached to the carbon atom at the 5-position of the benzodiazepine ring. "A" bearing an oxygen atom in the new heterocyclic ring may be formed from the corresponding 4,5-unsaturated benzodiazepines by treatment with an epoxide compound in the presence of an acid catalyst. "A" bearing either a nitrogen or an oxygen atom in the new heterocyclic ring may be prepared by cyclization of the corresponding open compound. "A" are useful as sedative, muscle relaxant and anti-convulsant agents.