The failure stresses in flexural tests of a densely sintered high-purity alumina (Procera AllCeram) were evaluated using three-point bend, ring-on-ring, and piston-on-three-ball tests. Glass-infiltrated presintered alumina (In-Ceram) and leucite-reinforced porcelain (IPS Empress) disks with the same dimensions were also tested using ring-on-ring and piston-on-three-ball tests. The failure stresses for all materials were substantially different (up to 50%) with different testing methods, and cannot be directly compared. However, by considering the effective specimen area under the maximum tensile stress, these failure stress data could be compared. The results emphasize the importance of knowing the test method and the method of calculation when comparing data. These three testing methods were also subjected to Weibull analysis. The Procera AllCeram had a consistently higher failure stress than the other two materials.