A cumulative damage procedure is developed to predict the fatigue failure of engineering metals subjected to complicated stress-strain histories. Histories with plastic strainings and cycles not completely reversed in stress are considered. The relationship between stress-strain behavior and fatigue life is investigated for unnotched axially loaded specimens for which the stresses and strains can be measured for the duration of all tests. Since either the stress history or the strain history was known before each test was conducted, the other could be estimated and a life prediction made. A general cumulative damage procedure is used to make life predictions for a wide variety of complicated history tests on 2024-T4 aluminum.