The aim. To study the clinical manifestations and features of changes in the spectrum of the bile acids in bile and blood in patients with non-alcoholic fatty liver disease. Materials and methods. 54 patients with non-alcoholic fatty liver disease at the stage of steatosis were examined. The median age was 50 years (45; 55). Complaints, objective symptoms and the results of laboratory and instrumental studies of the liver were used to verify non-alcoholic fatty liver disease. The content of the bile acids in bile and blood was determined using an AmazonX mass spectrometer (Bruker Daltonik GmbH, Bremen, Germany). Results. The majority of the examined patients (77,8%) with non-alcoholic fatty liver disease had subjective and objective symptoms of damage to the hepatobiliary system and intestines. According to the results of mass-spectrometry, a decrease in the total amount of primary free bile acids (cholic, chenodeoxycholic) and an increase in the total content of conjugated bile acids (glycocholic, glycodeoxycholic, taurocholic, taurodeoxycholic, ursodeoxycholic) in portions “B” and “C” bile, as well as blood compared with the control group. The concentration of acids conjugated with glycine was higher than that of taurine conjugates, while the correct ratio of glycine conjugates to taurine was observed (3: 1 and higher). Conclusion. Changes in the spectrum of the bile acids in bile and blood, firstly, is an indicator reflecting the violation of enterohepatic circulation, and, secondly, demonstrates the increasingly obvious importance of the bile acids in the pathogenesis of non-alcoholic fatty liver disease.