Clarification of the aetiology of chronic human diseases such as atherosclerosis or cancer is one of the dominant topics in the contemporary medical research. It is believed that identification of the causal factors will enable more efficient prevention and diagnosis of these diseases and, in some instances, also permit more effective therapy. The task is difficult because of the multistep and multifactorial origin of these diseases. In this paper the author attempts to review the present methodological approaches to aetiological studies of chronic diseases and discusses the role of criteria for identifying causal relationships.

        Key words: causality in medicine, chronic diseases.