Epirubicin (Farmorubicin) is a drug of significant interest in the treatment of a variety of solid tumours and a comprehensive review of reported investigations is given. From experimental and clinical studies it appears that in general doxorubicin and epirubicin exhibit no qualitative, but only some quantitative, differences. Thus, the pharmacokinetic and pharmacodynamic characteristics of the two drugs are essentially similar, as are the tumour spectrum and the level of their clinical efficacies. To achieve haematological equitoxicity of the two drugs the dose of epirubicin should be approximately 20% higher than that of doxorubicin, giving rise to a higher cumulative dose of epirubicin. On the other hand, epirubicin is significantly less cardiotoxic than doxorubicin. Thus, the recommended cumulative dose of doxorubicin is 500 mg/m2 and the corresponding figure for epirubicin is 1,000 mg/m2. For either drug a number of questions are still left open, the most important of which include the questions about optimal treatment schedules and the existence of a clinical relevant dose/efficacy relationship.