Polychemotherapy (CMF or CMF-like regimens) is the treatment of choice in premenopausal breast cancer patients with 1-3 positive nodes. In clinical practice, patients with abnormal biochemical tests of liver function are usually excluded from this potentially curative methotrexate-containing regimen in order to avoid worsening of hepatic damage. On the other hand, recent reports have shown a beneficial effect of methotrexate in a particular autoimmune liver disease such as primary biliary cirrhosis. We discuss the case of a female patient with breast cancer and primary biliary cirrhosis whose biochemical tests of liver function and the titer of antimitochondrial antibody persistently improved after treatment with 3 cycles of CMF. In conclusion, we suggest that the CMF regimen is potentially useful in patients with breast cancer and primary biliary cirrhosis.