The fracture toughness of a sintered reaction-bonded silicon nitride was measured by the single-edge precracked beam and surface crack in flexure methods, which are two of the three complementary test methods in ASTM C 1421. Results were compared with chevron-notched beam results that were available from another source. Precracks ranged from tiny artificial flaws introduced by Knoop indentation to millimeter-long precracks in single-edge precracked beams. The fracture toughness values from the three methods were in good agreement at 5.6 MPa(.)m(1/2).