[en] The so called human errors have always been apart of the everyday life of the mankind. In that sense, the discussion on man has a contributor to the operational safety of nuclear power plants is nothing new. It is interesting, that there do not exist widely accepted definitions of the human error nor the human reliability. Some of them are discussed at the beginning of this article. The second Chapter discusses the past and today of the research of man as a contributor to safety. Similarly, the development of Human Reliability Analysis (HRA) is described. The article, then, discusses the methods used in the contemporary HRA. The division between the identification of important human activities and their probability estimation is made. Especially, the pros and cons of the approaches and data sources used in the HRA are reviewed on a coarce level. At the end, a view on the use of expert judgment is given. The human behaviour has been an endless topic of research in the history - and will be it in future as well. In the conclusion of the article an opinion is given on the development during the past 30 years. Then, a rapid view on the possible future of the area is given. (orig.)