The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25°C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results areC11=13.7,C33=8.11,C44=3.50,C12=4.82,C13=5.68, andC14=−2.00, in units of 1011dyn/cm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception ofC13, these values substantially agree with the data of Voigt and Bhimasenachar.