A complete analysis is given of the propagation of acoustic waves in crystals of the tetragonal system. The determination of the elastic constants from measurements of longitudinal‐ and shear‐wave velocities in selected directions is discussed and experimental results for calcium molybdate are presented. The elastic constants in units of 1011dyn/cm2at 25°C are found to bec11=+14.47 ±2%,c33=+12.65±0.17%,c44=+3.69±0.17%,c66=+4.51±5%,c16=+1.34±50%,c12=+6.64±50%,c13=+4.46±2%.