In order to show the limits of medical experimentation the author traces the way covered by medicine in its aspiration to attain today's state of knowledge and therapeutic possibilities. The path of investigations begins in remote antiquity, proceeding through long years of observation and above all experimentation. Experiments broaden our knowledge and bring therapeutic effects, but often also cause pain, aggravation of illness and even death. The article discusses the problem of fighting contagious diseases such as Bubonic plague, cholera and smallpox, by undertaking attempts at preventive vaccinations which were to save the lives of millions of people in the future. It is described how progress was made in terms of knowledge of the human body in spite of objections on the part of some circles and frequently even condemnation of the researchers. The discovery of bacteria and viruses was a real breakthrough in fighting epidemics. Incessant efforts to find methods of quick diagnosis, correct treatment and rehabilitation are described. The downsides of discoveries are discussed as well: the cobalt bomb on the one hand, and the atom bomb on the other. Experimentation is the basis of progress in medicine, but the medical experiments of Nazi doctors or Soviet psychiatrists brought disgrace to the medical profession. Other issues tackled in the article include problems of transfusiology and organ transplants, as well as those of genetics, genetic engineering or cloning. Attention is also drawn to patient rights and rights of persons subjected to a medical experiment. The ongoing debate in the medical world and denominational circles on the limits of medical experiment is highlighted. Last but not least, the author looks at the legal aspects of the problem of experiment raised by forensic physicians and lawyers. The final conclusion that follows from the study is that there is no univocal answer to the question about the limits of medical experimentation and each person concerned must seek their own answer as it depends on many of the aspects mentioned above.