The adiabatic elastic constants of aluminum have been measured with an ultrasonic pulse technique at liquid‐heluim, liquid‐nitrogen, and room temperatures. The values of the elastic constants at 4°K arec11=11.63,c12=6.48, andc44=3.09 in units of 1010N/m2. The Debye characteristic temperature calculated from these figures is &thgr;=425°K in good agreement with the value obtained from speciffic heat data.The shear elastic constants ½(c11−c12) andc44are discussed with reference to the theory given by Leigh.