[Clinical trial under trial. 'Trial and error'].

Randomized controlled clinical trials are being exposed to severe criticism in recent years. It is questioned if the use of placebos in such trials is ethically justified. This and other ethical problems will be discussed in this paper. Ethical problems include, besides the use of placebos, obtainment of informed consent and the belief in 'treatment indifference'. Beforehand a historical overview is presented and the design of the randomized controlled clinical trial is explained. Some other types of clinical trials will also be touched upon.