A patient with breast cancer developed severe asthenia, accompanied with progressively increasing transaminases, during adjuvant chemotherapy with CMF (cyclophosphamide, methotrexate and 5-fluorouracil). Additional blood tests and imaging were negative. A liver biopsy revealed a grade II toxic hepatitis. Because methotrexate was suspected to be the cause of the hepatotoxicity, the administration of this drug was stopped and mitoxantrone was given instead. A recovery of clinical symptoms and normalisation of the liver function tests was observed afterwards. In that sense, mitoxantrone appears to be a valuable alternative to methotrexate in cases of hepatotoxicity in patients with breast cancer. An overview of the literature regarding methotrexate hepatotoxicity is presented.