A method of predicting lifetime to failure for any wood composite system subjected to a complex load-time history has been developed. The prediction first requires the generation of a simple model to characterize the fatigue response of the particular composite system and a rainflow analysis breakdown of the load-time history under investigation. Once the models a re derived they can be used to predict lifetimes to failure for any load-time history using a modified Palmgren-Miner damage summation rule. Variable amplitude fatigue testing of sample material using the same load-time histories allowed a comparison to be made between predicted and actual lifetimes to failure and was useful in verifying and refining the life prediction models.