High-Lite S-1005 lenses (Schott Optical Company) of various center thicknesses were tested for static load fracture resistance. Chemically tempered High-Lite lenses of 1.7-mm center thickness were found to be equivalent in strength to 3.0-mm heat-tempered crown lenses; 1.34-mm chemically tempered High-Lite lenses were equivalent in strength to 2.07-mm heat-tempered crown lenses. These findings agree closely with earlier data on chemically tempered crown glass and therefore illustrate that chemically hardened lenses can be made significantly thinner than Z-80 specifications and still meet FDA strength requirements.