Abstract: A conventional dynamic testing machine, such as an MTS (Material Test System) is modified to allow for a new method for dynamically monitoring fatigue damage in a specimen. Load and stroke signals are used to determine phase angle and gain frequency response parameters for a specimen as it is cyclically loaded. Although the cycles required for specimens to fatigue to failure varies greatly from specimen to specimen, the phase shift between the load and stroke signals as well as the gain of the stroke signal remains fairly constant from specimen to specimen. These characteristic parameters can be used to accurately determine the percent of life remaining and residual strength in other specimens.