Ethical questions in trials in humans are particularly urgent today for many reasons. Basic concepts and recognized ethical requirements are presented. The role of medical statistics and planning of trials for ethical questions is discussed with the example of estimation of case numbers. Human suffering is kept as low as possible, the framework of thought for sophisticated ethical questions is first prepared by calculation, statistics contribute to the objectivation of facts and the obtaining of consent and open up new ethical problems. A check-list of questions that should be raised in a trial on humans and a compilation of the ethical problems to be expected nowadays are given. Theses on the ethics of human trials close the paper.