Abstract: A chimney access door assembly for mounting on existing chimneys to permit convenient cleaning includes a frame member defining an aperture therein and which is mounted in the opening of the chimney and a closure member dimensioned to overlie and close the aperture in the frame member and extend about a marginal portion of the frame member about the aperture. Gasket means is provided between the adjacent surfaces of the closure member and frame member and extends about the frame member aperture so as to substantially prevent passage of smoke, fumes and the like. In one embodiment, the closure member is provided with a recess for seating on its inside surface insulating means for use of the access door assembly on an exterior wall.