The elastic moduli of cadmium telluride at 25°C have been determined by measurement of ultrasonic wave velocities in the frequency range 40–300 Mc/sec. Preparation of the crystal specimens is described, and factors affecting the accuracy of results are considered. The question of possible piezoelectric stiffening and its effect on measured wave velocities is also considered. Based on a density of 5.854 g/cm3as computed from the lattice constant (and taken as exact with respect to uncertainty estimates) the zero field elastic moduli are:ModulusValue d/cm2Uncertainty in %c115.351×10110.15c123.6810.2c441.9940.15