Standard Reference Material (SRM) 2100 is the first reference material in the world for the property fracture toughness. The SRM was developed in tandem with the new ASTM test method C 1421-99. The SRM also supports two International Standards Organization (ISO) draft standards now under development in ISO Committee TC 206, Fine Ceramics. The SRM is a set of five silicon nitride test specimens. The SRM may be used with any credible ceramic fracture toughness test method, but has been optimized for test methods that use beams in bending. Identical results are obtained with single-edge precracked beam, chevron-notched beam, and surface crack in flexure methods. SRM 2100 should dramatically improve fracture toughness testing and enhance data quality around the world. This paper describes SRM 2100 and its creation.