A DOOR OPERATOR ADAPTED TO MOVE AN UPWARDLY ACTING DOOR ALONG TRACKS BETWEEN OPEN AND CLOSED POSITIONS. THE OPERATOR INCLUDES A CARRIAGE MOUNTED UPON A SUBSTANTIALLY HORIZONTAL RAIL EXTENDING PERPENDICULARLY AWAY FROM THE CLOSED POSITION OF THE DOOR. AN ENDLESS CHAIN IS ARRANGED IN AN ELONGATED LOOP EXTENDING ALONG THE RAIL AND SUPPORTED FOR MOVEMENT RELATIVE THERETO. ONE END OF THE LOOP CAN ROTATE A SHAFT MOUNTED ABOVE THE CLOSED POSITION OF THE DOOR. CABLES ARE CONNECTED BETWEEN THE SHAFT AND THE LOWER EDGE OF THE DOOR. DRIVE MEANS ON THE CARRIAGE ENGAGES THE CHAIN AND CAUSES THE CARRIAGE TO MOVE RELATIVE TO THE CHAIN AND THE RAIL. LINKAGE CONNECTS THE CARRIAGE TO THE DOOR AND COOPERATES WITH THE CABLES FOR OPENING AND CLOSING THE DOOR.