The concept of eco-efficiency is examined using a materials perspective. New insights are uncovered regarding the assessment and interrelationship of natural resources, materials and products. With this new understanding, the paper pro- poses management strategies for eco-efficiency that differentiate between different materials. From this, a framework for evaluating eco-efficiency models is derived, and is then used to evaluate seven popular eco-efficiency models in use by decision makers today. Section 1 introduces eco-efficiency and identifies some general issues related to eco- efficiency models that have led to this work. Section 2 begins with a scientific analysis of different natural resources and materials, and then illustrates how a better understanding of the chemical and physical properties of materials can help guide environmental improvements. Section 3 incorporates the understanding of materials and eco-efficiency into an evalua- tion framework, and provides criteria with which to evaluate the scope of eco-efficiency models. Section 4 evaluates seven popular eco-efficiency models using the Eco-efficiency Model Evaluation Framework developed in Section 3. Section 5 summarizes the findings and indicates directions for the ongoing development of eco-efficiency models to ensure their continued usefulness.