One-third of the breast cancer patients who underwent tamoxifen intake showed less than 0.9 of their liver/spleen CT (computed tomography) ratio on their annual CT study, and were diagnosed as having fatty liver (hepatic steatosis). Among them, patients who showed a lower liver/spleen CT ratio of less than 0.5 were recommended to undergo needle biopsy of the liver in order to obtain histopathological confirmation of non-alcoholic steatohepatitis (NASH), with 15 patients undergoing needle biopsy of the liver. As a result, 14 out of the 15 patients were diagnosed as having NASH, and these patients were additionally administered bezafibrate in order to prevent possible progressive changes of NASH into liver cirrhosis. In this study, we show the changes of follow-up CT findings of 6 patients with histopathologically-proven NASH who continued to undergo bezafibrate intake after the diagnosis of NASH. Two patients showed almost complete improvement as indicated by the liver/spleen CT ratio several months after completion of a tamoxifen intake of 5 years, and another 3 showed partial improvement on their liver/spleen CT ratio by bezafibrate intake in spite of continuing tamoxifen intake. Another patient with diabetes mellitus (type II) showed a continually decreasing liver/spleen CT ratio during adjuvant tamoxifen in spite of bezafibrate intake. Therefore, we concluded that the progression of NASH could be prevented by bezafibrate without any interruption of adjuvant tamoxifen treatment. For patients with diabetes mellitus, critical follow-up using CT study and laboratory tests is considered essential.