Abstract: A unitary weatherstripping and self-balancing sash guide for slidingly embracing the juxtaposed side edges of a pair of double-hung inner and outer window sash units, and guiding their sliding opening and closing movement in a window opening, comprises an arched portion spanning the side edge of the window opening and having a central parting bead protruding into the window opening, inner and outer terminal flanges protruding from the arched portion into the window opening, and two slanting wing flanges respectively extending cantilever-fashion from the parting bead diagonally toward the arched portion and the respective terminal flanges, forming therewith a pair of channel-shaped grooves each embracing the side edge of one sash unit, whereby each of the two sash units is slidingly gripped in resilient tractive balancing engagement between a terminal flange and a facing slanting wing flange resiliently deformed by the embraced sash unit.