Abstract: A sash window includes a fixed frame in which at least one inner sliding frame can slide between an open position and a closed position of the window, and at least one sliding or fixed outer frame, seals being interposed between the fixed frame and the inner sliding frame, a sealing system including, for the inner sliding frame, two lateral seals, a top cross-member seal, for the outer frame, and a bottom cross-member seal. Additionally, the invention the sealing system includes intermediate seals that join on each side of the sliding frame the cross-member seals and the lateral seals, so as to form a continuity of sealing between these seals in the closed position of said inner sliding frame. The lateral junction region between the inner sliding frame and the outer frame is thus connected by a sealing system that makes them sealed vis-à-vis each other.