[Primum non nocere--what does it mean in medicine today?].

The study analyzes bioethical principle of Primum non nocere and its importance and value in modern medicine. The criterion of maleficence for a patient, is defined in its real and ethical, individual, general and time contexts. The relation of ethical postulates of non-maleficence and beneficence and their correlation have been studied. The attention has been drawn to the inadequacy of isolated criterion of causing damage (non nocere) to secure benefit for a patient. The study expresses the necessity and obligation of medicine to estimate scientifically old and new perceptions and applies them to a patient, consonant with bioethical principles.