This report is organized into two parts. Part I presents the synthesis of literature and practice related to multiple-use trails. It is organized around the three major challenges faced by trail managers and the two categories of responses at their disposal to address these challenges. In every case the challenges and available responses cut across many trail activities and types of trails. Part I concludes with a presentation of general principles for avoiding and minimizing conflicts on multiple-use trails distilled from the information reviewed. Part II builds on the synthesis by identifying gaps in our current knowledge and suggesting research that could be undertaken to close these gaps.