Abstract: A method for measuring fracture toughness of a brittle material is described which comprises the steps of impacting a sample of the material of preselected thickness and predetermined density and characteristic ultrasonic wave velocity C.sub.i at preselected velocity with a projectile of material having a known density and characteristic shock impedence corresponding to a predetermined characteristic ultrasonic wave velocity, determining the stress .sigma. at which the sample fractures upon impact of the projectile, and determining the fracture toughness of the sample as equal to 2.sigma.(c.sub.i t/.pi.)1/2, where t is the calculated time duration of a tensile pulse traveling the thickness of the sample.