A case of toxic liver disease induced by cyanamide in a patient in treatment with this drug during 18 months, is presented. We reviewed the different liver cell alterations produced by a long-term treatment with cyanamide, which produces fibrosis and portal inflammation, as well as polished cells with different characteristic features. These alterations forced the establishing of close controls of patients in treatment with this type of anti-alcoholism drug, as well as the reduction of the duration of therapy, this questioning the efficacy of the treatment of chronic alcoholism with this aversive drug.