The intestinal microbiota is a microenvironment that has been the subject of studies for several decades. Over time, it has been reconsidered as a possible cofactor of multiple acute and chronic human diseases. In fact, alterations of the intestinal bacterial flora have been found in various neurological diseases. There are three modes of interaction between the intestinal microbiota and the gut-brain-axis: chemical signals, neural pathways and immune system. Even at the gastrointestinal level, the gut microbiota plays certainly an important role in the etiopathogenesis of chronic intestinal inflammatory diseases but also in irritable bowel syndrome. An important correlation has also been demonstrated with non-alcoholic fatty liver disease, as well as in other metabolic, cardiovascular and oncological diseases. Bacteria, viruses, fungi and various microorganisms that normally reside in our intestines can also be called into question as protective factors against these diseases. All this evidence leads researchers to consider the gut microbiota as a key element in the determination of aforementioned diseases. Therefore, it would be foreseeable in the future to associate the use of probiotics with the therapies used in the treatment of all these diseases. In this review we have condensed the main current knowledge regarding the link between the most frequent diseases and the gut microbiota.  Kulcsszavak: gut microbiota, metabolic diseases, cardiovascular diseases, inflammatory bowel disease, dysbiosis, NAFLD