This paper presents the results of collaboration to develop tools for the prediction of plastic gear tooth failure for any given set of operating conditions and to classify failure modes of these gears. The goal of the project is to characterize and predict the failure of plastic gears over a range of given parameters. A test plan was developed to explore the effect of rotational speed@ root stress@ and flank temperature on the life of plastic gears. The dependent variable for the experiments was the number of cycles (or rotations) until failure.