Community-Led Total Sanitation is an approach to create community-wide sanitation and hygiene behaviour change. The CLTS approach has been scaled rapidly to over 50 countries, but limited rigorous evidence on cost-effectiveness and scalability has been generated. The Testing CLTS Approaches for Scalability project is a four-year partnership between Plan International and the Water Institute at the University of North Carolina to collect, criticality evaluate, and disseminate practical lessons learned about implementing CLTS at scale. Learnings are based on rigorous applied research from a systematic literature review and a variety of research activities in 12 countries. This briefing shares a summary of the project, the research designs used, and preliminary findings