Anorexia nervosa (AN) is a psychiatric disorder related to very serious consequences for physical and mental health of patients. Due to a complex clinical picture, which consists of anumber of somatic and mental symptoms, AN remains a serious problem of modern medicine and encourages the search for possible causes of the illness and new, more effective therapies. The recent reports emphasize the role of the intestinal microbiota in regulation of body weight. In this light, the hypothesis that in AN patients there is a significant imbalance of the intestinal microbiota, which contributes to the pathogenesis of the illness, seems interesting. The results of the latest research suggest that abnormal composition of the intestinal microbiota may be an important factor supporting cachexia of AN patients. Detailed analyzes of the composition of the microbiota characteristic for anorexia nervosa could be useful in developing new methods for monitoring and treatment of this illness. This paper aims to present the current state of the art about the role of the intestinal microbiota in the pathogenesis, course and treatment of AN.