Interest in procedural fidelity has grown rapidly since 1981 as evidenced by the growing numbers of research publications across disciplines on this topic. As a result, the past 30 years of research has yielded a variety of procedures to guide research and practice, which we hope translates into better educational practices and services. Despite our progress, much remains unknown. As an introduction to the special issue on advancements in procedural fidelity, this article will briefly describe the conceptual and definitional issues surrounding this topic, summarize the relevance of procedural fidelity to education and research, and highlight the articles in this issue that address proposed research priorities.