Abstract: Thermally toughened glass sheets of thickness 2.5 mm to 3.5 mm, for use as motor vehicle side or rear windows, are produced by differential quenching producing a distribution of regions of more highly toughened glass interspersed with regions of lesser toughened glass. The average central tensile stress is in the range 62 MN/m.sup.2 to 53 MN/m.sup.2, and there is a distribution of areas in which the principal stresses acting in the plane of the glass sheet are unequal. The principal stress difference in some of the areas is at a maximum in the range 8 MN/m.sup.2 to 25 MN/m.sup.2, the major principal stresses in adjacent areas in which the principal stress difference is a maximum are in different directions, and the distance between the centers of such adjacent areas is in the range 15 mm to 30 mm.