Abstract This paper discusses the results of thirty-nine in-plane loading tests on single window panels under a horizontal in-plane force applied to the horizontal top member of a steel, pin-connected, or hinged, loading frame. Under this load condition the movement of the glass with respect to the sash as well as the horizontal in-plane deflection, or drift, of the window panel, fastened to this hinged frame, were measured by means of dial gages. Panel size and panel configuration Panel attachment to hinged frame Sash material Clearance between glass and sash Hardness of putty Thirty-three specimens were tested under static loads. Two tests were performed under repeated reversed loads and four under impact loads. Some conclusions were derived regarding the ultimate drift of a window panel under the load conditions used and as affected by the variables listed.