Developed from the authors’ courses taught to public health and medical students, residents, and fellows, this text shows how biostatistics in clinical trials is an integration of many fundamental scientific principles and statistical methods. The authors cover design concepts and sample size calculation; analytical methods; trial monitoring with sequential designs, interim analyses, and adaptive midcourse modification; and the ubiquitous problem of missing data. The text includes many examples of real trials as well as homework assignments and in-class exercises.