This book provides a state-of-the-art review of the life-limiting mechanisms of geosynthetics, the methods available to test and assess lifetime, and the means by which durability can be improved. It provides engineers with the information they need on the durability lifetime, bridging the knowledge gap between them and polymer scientists. The style of the handbook is deliberately non-technical, in that it avoids chemical formulas and makes widespread use of graphs and photographs. Summaries are provided for most sections. It shows how to predict the service life of geosynthetics based on state-of-the-art knowledge and in some cases provides numerical examples. Engineers can use it to decide what they should specify, scientists are shown how to perform extrapolations and derive reduction factors, and assessors are given a separate section indicating how they should treat the information presented to them, including the uncertainties of the methods of testing and extrapolation. While directed primarily at geotextiles, reference is made to geomembranes and their use in landfills, for which a supplementary chapter is added.