The avg. size of the specimens to be tested in compression was approx. 4.5 mm. long and 1.8 mm. in diameter. Samples were obtained with special hollow drills from freshly extracted 1st and 2d molar teeth kept wet during the entire operation until time of test. The avgs. of the physical properties of dentin are: modulus of elasticity, 1.67 x 106 psi, proportional limit, 23,400 psi, compressive strength, 36,100 psi. The physical properties are influenced by such variables as physiological differences in the teeth tested, directional effects in the tooth structure, rate of stress application, length to diameter ratio of the specimens, and soundness of specimen. The values obtained represent useful values for the analysis of stresses and subsequent movement in restorations and teeth.