Two female breast cancer patients who received combined tamoxifen and tegafur as postsurgical adjuvant therapy developed severe hepatotoxicity after being treated for three and eight months, respectively. Shortly after the cessation of the treatment, routine liver tests showed gradual recovery, but liver biopsies revealed chronic active hepatitis in one patient and liver cirrhosis in the other. Four and five years, respectively, after the cessation of the treatment, the results of liver tests were normal and distinct histological improvement was observed in both patients. Because these patients had no viral and immunoserological markers nor any history of alcohol abuse, this study suggested that the tamoxifen and tegafur regimen induced reversible chronic active liver disease.