This book is a comprehensive and practical introduction of clinical epidemiology for students and practitioners. It covers both the basic principles and concepts of clinical epidemiology as well as its applications in various medical disciplines. It covers how to design, conduct, and interpret clinical studies using methods such as bias analysis, confounding control, causality assessment, diagnosis evaluation, prognosis prediction treatment comparison, and meta-analysis in this book. It also introduces how to apply these skills to real-world scenarios through case studies and examples that provide a fresh perspective on familiar topics. This book is a useful textbook for graduate and undergraduate students in medical schools, as well as a valuable reference for medical teachers and practitioners.