Process tracing (PT) involves a detailed analysis of the processes that link interventions to outcomes. PT is particularly useful for evaluating interventions that are difficult to quantify, such as knowledge work or institution building. It involves creating a detailed causal theory, tracking the process theory of change (pToC) by examining the observable evidence, and learning general lessons from the cases studied. PT offers two main benefits to evaluators: first, it provides a clear way to present and evaluate the strength of the evidence collected. This helps in making the evaluation process more understandable and credible. Second, it helps evaluators learn practical lessons more easily by emphasizing the explicit connections between actors, their actions, and resulting behavioral changes. However, the reliability of findings from PT depends on how well the theory matches the observable evidence. This paper explains how process tracing (PT) is a valuable tool for evaluating policy changes and program effectiveness. It details the methodology, highlights the importance of tracking processes and events linking interventions to results, and discusses PT's advantages and limitations. The paper provides a step-by-step implementation guide and examines the use of PT in an anonymized IEG evaluation as an example
