['To examine the ultrastructural changes after ursodeoxycholic acid (UDCA) treatment in hepatocytes from experimentally induced fibrotic livers.', 'Liver fibrosis was induced in male Sprague-Dawley rats with CCl4 for 12 wk, and the rats were divided into two groups. Group I was treated with saline and group II with UDCA (25 mg/kg per day) for 4 wk. All the rats were killed at wk 16. Mitochondria, nuclei, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) of hepatocytes were evaluated according to a scoring system.', 'Mitochondria, nuclei, RER and SER injury scores in group II were significantly lower than those in group I (P < 0.001).'] Does ursodeoxycholic acid treatment improve hepatocyte ultrastructure in rat liver fibrosis?