Abstract: A pet door assembly for mounting over an opening includes a box containing a pivot arranged to be positioned beside the opening and such as to extend perpendicularly to the plane of the opening, and a door mounted on the pivot so as to be movable in its own plane between positions in which it opens and closes the opening. A rotary electric drive device such as a rotary solenoid are provided for swivelling the door between the open and closed positions, and a sensing device is provided which is operable by a pet for causing actuation of the drive device to open the door. Preferably, a tunnel is provided by tubular members which are separated by a gap in which the door can move, and weather stripping may be provided between the door and the adjacent ends of the tunnel members. For better insulation, the door may comprise 2 spaced apart planar members which are mounted to move together.