[Principle and practice of clinical phase III studies].

Randomized phase III studies compare new treatments with standard therapy according to defined guidelines and legal rules. Large international randomized phase III studies are some of the most complex and expensive medical experiments. The results of such trials will decide about the future of new drugs and are the basis of evidence-based medicine and the development of clinical guidelines. This contribution discusses randomization, endpoints, inclusion and exclusion criteria of phase III trials as well as further challenges when developing and conducting phase III studies in oncology.