The aim of the study – to explore the gut microbiota composition and its association andcorrelational relationship with biochemical factors in patients with nonalcoholic fattyliver disease (NAFLD) compared to the patients without liver disease.Materials and methods. 154 patients with NAFLD and 83 controls were included intothe study. The examination involved the biochemical parameters, ultrasound data,elastography, identification of gut microbial composition by real-time PCR. Patients ofboth groups were matched by patients charasteristics.Results. There was higher level of Bacteroidetes in group of patients without NAFLD.Actinobacteria range and Firmicutes/Bacteroidetes index (F/B index) in patients with NAFLDwas above in comparison with patients of control group. Age and BMI are the risk factorsfor NAFLD development. Actinobacteria in NAFLD group positively correlated with Tumornecrosis factor alpha (α), while F/B index was in strong relationship with ALT, TG, VLDL. TheF/B index was in negative correlational relationship with TNF-α in group without liver injury.Conclusions. The composition of the intestinal microbiota is different between groupof patients with NAFLD and controls. Actinobacteria and F/B index growth could bediscussed as one of the risk factor for the fatty infiltration development in patientswith NAFLD, taking to account the fact that F/B index could be associated with suchinflammation markers as ALT and TG. Simultaneously, the same microbiome phyla couldbe the potential prevention factor of lipid disorders in patients without liver injury.