The use of substitute materials for historic preservation is not new. For decades, preservation practitioners have turned to substitutes under various circumstances, including the unavailability of historic materials or craft techniques, or when a substitute material offers equal or superior performance and durability at a lower cost. In coming years, the growing emphasis on sustainability and the decreasing availability of natural historic building materials, as well as the implications of preserving mid-to-late 20th century modern architecture, may lead to more frequent use of substitute materials for the preservation of historic buildings. Through a comprehensive review of published preservation literature and a survey of 250 preservation practitioners, this thesis seeks to answer the following questions: (1) Is adequate guidance available for the evaluation and selection of substitute materials? (2) What considerations are necessary when evaluating and selecting substitute materials? (3) Is a new method necessary to better equip preservation practitioners to make decisions about substitute materials within the framework of preservation philosophy, material properties and performance, economics, and sustainability? The result is a comprehensive inventory of considerations which provides an organized and systematic approach to material characterization and evaluation, as well as suggestions for a method that can be used by practitioners to select (or reject) substitute materials within the context of preservation philosophy, material properties and performance, economics, and sustainability. This guidance, together with long-term performance assessments and the development of a resource for the dissemination of material performance data, should inform and improve the future use of substitute materials.