This book offers a practice-oriented introduction to the methodological foundations of clinical trials in scientific research and the pharmaceutical industry. The fundamental principles of planning and conducting clinical trials, as well as the key statistical methods for their evaluation, are presented and explained in an understandable manner. In addition to the methodology for therapeutic studies, the authors also address the specific procedures in diagnostic and prognostic studies. Using examples from concrete studies, primarily from their own work environment, the authors vividly illustrate the principles and methods and exemplify the problems that arise in practice. Furthermore, they discuss historical developments and the internationally applicable standards for the quality of clinical trials. The book is aimed at anyone who wishes to conduct clinical studies.