Book excerpt: This guidebook provides a practical synthesis of the best available science for using beaver to improve ecosystem functions. If you are a restoration practitioner, land manager, landowner, restoration funder, project developer, regulator, or other interested cooperator, this guidebook is for you. Our overall goal is to provide an accessible, useful resource for those involved in using beaver to restore streams, floodplains, wetlands, and riparian ecosystems. Although the guidebook summarizes current information about how to use beaver in restoration and conservation, the knowledge base on this subject is rapidly expanding. This means that not all of the information provided has been peerreviewed in scientific journals; some of it is instead based on the real-life experience of restoration practitioners who are conducting ongoing experiments on using beaver to restore habitat. Thus the guidebook is a compilation of the current best available science, and we expect to update it regularly as the science progresses, readers provide information from their ongoing restoration experiments, or from restoration efforts of which we are currently unaware. See Table 1 for the different types of data presented in this document and the relative ranking we used for assessing scientific credibility. Much of the information presented here is applicable across the beaver's range, but the guidebook focuses on beaver restoration in the western United States. Much of the interest in beaver restoration is occurring in the context of restoring habitat for declining populations of Pacific salmon and trout while simultaneously improving stream flows, particularly in drought-prone regions.