Abstract: A metal door frame assembly comprising two jambs and a lintel, all of the same crosssectional shape, which includes a central door striker portion flanked on its two sides by an inner web and an outer web respectively, each web terminating in a respective end flange which itself terminates in a inturn flange, each inturn flange terminating in an returned flange. Assembly of the jambs and lintel is effected by mitre joints, and at each mitre joint there is a bridging strip which extends between the facing surfaces of the end flanges, and which bears against the rear surfaces of the inner and outer webs of the jamb and lintel. The bridging strip is retained in position by a pair of locking plates, each of which has a pair of tabs which engage respective apertures in the returned flanges of the jamb and lintel.