Abstract: A two-way envelope has a front and rear surface formed of a single rectangular sheet folded upon itself about a transverse central foldline. The envelope comprises overlying front and rear return envelope panels, overlying front and rear data bearing panels, and front and rear transverse lines of separation parallel to the central transverse foldline and separating the return envelope panels from the data bearing panels. The transverse lines of separation are offset to define on one surface of the envelope a return envelope flap adjoining one of the return envelope panels by a line of weakness. Adhesive is disposed on the inner surface of the return envelope flap, and sealing means secures the three free edges of the two-way envelope about the central foldline except those portions of the edge coincident with the return envelope flap.