Book excerpt: This report summarizes the proceedings, including key points and identified research needs, that evolved from the Mass Timber Research Workshop, which was held at the USDA Forest Products Laboratory (FPL), November 3-4, 2015. The purpose of the workshop was to bring design professionals, researchers, and industry leaders together to examine the state-of-the-art in mass timber construction, with an emphasis on cross-laminated timber, and to identify technical barriers to the broader use of wood in engineered structures that need to be addressed. Following a plenary session on mass timber in North America, some 120 scientists, engineers, and industry leaders heard presentations organized in four technical areas: (1) resistance to lateral loads, (2) building performance-durability, sound, vibration, and life cycle assessment, (3) fire safety, and (4) material resources and other research topics. Breakout sessions aimed at identifying future research objectives were then held for each of the four technical areas, followed by a prioritization of future research needs. Included in these proceedings are abstracts from each presentation, copies of all presentations and a summary of research needs.