"This paper presents comparative learning from the evaluation of six international development initiatives that applied various forms of Process Tracing. While these initiatives span across diverse contexts and pursued different aims, they are connected by a common thread: all six case studies centre around efforts to influence others - often decision makers and those in power - around aspects such as practices of consultation and inclusion; public policy; and resource allocation. The paper is organized in the following manner. We first explain Process Tracing and review common definitions. Secondly, we consider the potential value added of an explicitly Bayesian approach to Process Tracing. Next, we discuss the six cases where Process Tracing was applied, noting similarities and differences. Then, we explore key practical learning emerging from the cases and insights from the use of different forms of Process Tracing across different programming contexts. These reflections are organized under four meta-themes of participation, Theory of Change, methodological decisions, and mitigating bias. Finally, we present our key recommendations, ending with practical tips, targeted at practitioners and evaluators interested in applying Process Tracing, especially for initiatives falling under the ‘influencing’ umbrella." (Introduction)