Models which designers use to predict fatigue under variable amplitude and random loading are summarized. Basic terminology associated with random process theory is presented. Models for computing fatigue damage associated with various statistical distributions of stress ranges are reviewed. The Palmgren-Miner rule is described and statistical summaries which provide a description of the performance of Miner's rule is presented. A closed form expression for fatigue damage under wide band stress spectra is given. Finally, methods of predicting fatigue crack growth under variable amplitude stresses are reviewed.