The last decade has seen a remarkable growth in the rated power of wind turbines throughout the world, particularly in Europe, with a 170m diameter 10MW turbine thought technically feasible by 2015. It has been an increasing challenge for the wind turbine industry to meet these technical requirements and in doing so the industry has employed a large amount of innovation in the detailed use of materials, design, analysis and testing. In this article, the authors propose a new damage tolerance methodology for the design and testing of wind turbine blades. This has the potential to radically reduce the test programme requirements for large wind turbine blades.