['\u2002 The data on the beneficial effect of ursodeoxycholic acid (UDCA) in non-alcoholic steatohepatitis (NASH) are controversial. The difference of opinion is connected with UDCA dosage to be used. Therefore, we evaluated the dose-dependent efficacy of UDCA in experimental NASH.', '\u2002 Male Wistar rats were fed the methionine- and choline-deficient (MCD) diet for 10\u2003weeks. Rats were administrated UDCA (10, 20, 40 and 80\u2003mg/kg bodyweight intragastrically) after 6\u2003weeks of the MCD diet.', '\u2002 Animals fed the MCD diet developed severe steatohepatitis. Treatment with UDCA dose-dependently decreased liver damage, but only high-dose UDCA (80\u2003mg/kg) significantly diminished ultrastructural changes in addition to preventing steatosis, ballooning and inflammatory changes in the liver. The activities of serum marker enzymes and the content of liver triglyceride and blood glucose were increased in MCD diet-fed rats, but decreased in all the UDCA-treated groups. Serum insulin concentration was decreased whereas the quantitative insulin sensitivity check index did not changed in MCD diet-fed groups. Serum tumor necrosis factor-α content was strongly increased after MCD diet and normalized in the UDCA-treated rats, with the most pronounced effect in the highest dose groups, 40 and 80\u2003mg/kg. The contents of endogenous ethanol in blood and intestinal mucus were increased in MCD diet-fed rats which were significantly lowered by UDCA (40 and 80\u2003mg/kg per day).'] Does ursodeoxycholic acid dose-dependently improve liver injury in rats fed a methionine- and choline-deficient diet?