This article by David Collier from the University of California, Berkeley, focuses on the method of process tracing, a fundamental tool in qualitative analysis. It highlights the importance of process tracing in both describing political and social phenomena and evaluating causal claims. The article aims to address the common issues of inadequate understanding and rigorous application of process tracing by scholars. It introduces a new framework that integrates discussions of process tracing and causal-process observations, emphasizes the role of description, and stresses the causal sequence in which observations can be situated. The framework is part of a broader effort to systematize qualitative methods, which can add inferential leverage often lacking in quantitative analysis. The article is accompanied by online teaching exercises that cover diverse substantive areas, including American politics, comparative politics, international relations, and public health/epidemiology. These exercises provide practical examples to illustrate the application of process tracing. The article also discusses the relationship between process tracing and causal-process observations (CPOs), emphasizing that careful description is a crucial foundation for process tracing. It outlines four empirical tests for causal inference: straw-in-the-wind, hoop, smoking-gun, and doubly decisive tests. These tests help researchers evaluate the strength of evidence and the plausibility of hypotheses. Finally, the article concludes by emphasizing the importance of process tracing in qualitative research and the need for further development and refinement of its tools. It highlights the value of process tracing in addressing challenges in both qualitative and quantitative research and encourages productive teaching and thinking about process tracing.This article by David Collier from the University of California, Berkeley, focuses on the method of process tracing, a fundamental tool in qualitative analysis. It highlights the importance of process tracing in both describing political and social phenomena and evaluating causal claims. The article aims to address the common issues of inadequate understanding and rigorous application of process tracing by scholars. It introduces a new framework that integrates discussions of process tracing and causal-process observations, emphasizes the role of description, and stresses the causal sequence in which observations can be situated. The framework is part of a broader effort to systematize qualitative methods, which can add inferential leverage often lacking in quantitative analysis. The article is accompanied by online teaching exercises that cover diverse substantive areas, including American politics, comparative politics, international relations, and public health/epidemiology. These exercises provide practical examples to illustrate the application of process tracing. The article also discusses the relationship between process tracing and causal-process observations (CPOs), emphasizing that careful description is a crucial foundation for process tracing. It outlines four empirical tests for causal inference: straw-in-the-wind, hoop, smoking-gun, and doubly decisive tests. These tests help researchers evaluate the strength of evidence and the plausibility of hypotheses. Finally, the article concludes by emphasizing the importance of process tracing in qualitative research and the need for further development and refinement of its tools. It highlights the value of process tracing in addressing challenges in both qualitative and quantitative research and encourages productive teaching and thinking about process tracing.