An apparatus for supporting a window sash (54) has clamps (14, 16) for clamping the support apparatus to a frame unit (52) of a window assembly (50) and support arms (42) mounted on the support apparatus for supporting the window sash (54) in an open position relative to the frame unit (52). The apparatus has the advantage that it allows a window sash of the type that opens outwardly of a building to be removed and/or installed from the interior of the building.