Abstract: A door for vehicles, mainly comprising a box structure with a downwards open cavity. An assembly formed by the glass and the relevant guides and lifting mechanisms is assembled separately and is then inserted from the bottom into the cavity of the box structure of the door, and fixed therein. The box structure of the door, which may advantageously be made of plastics, is further provided with a recess into which a lock assembly, separately assembled as well, can be inserted. The lock actuating structure can be housed within a recess particularly provided to this end in a protrusion forming an arm rest. With these arrangements, the expensive operations which have to be performed on the door installed on the vehicle are minimized, thus reducing the assembly costs and time.