Tensile and compressive fatigue tests were conducted by means of pulsating loading. Results showed that the cyclic number to failure in compression was larger than that in tension and a longer time for fracturing was required for the higher frequency when stresses were the same. A comparison between fatigue fracture and static fracture, on the basis of time for fracturing, showed that tensile fatigue fracture occurs in a shorter time than static fracture, whereas compressive fatigue failure takes a longer time than does static failure. The mechanical-loss tangent at high stress amplitude gives a higher value in compression than tension; both values tend to become equal at low stress. The av. energy loss per unit cycle consists of 2 parts (energy loss concerned with fractures and that not concerned with fractures).