Trimethoprim-sulfamethoxazole (co-trimoxazole) is used extensively for treatment of pulmonary and urinary tract infections. Side effects may affect skin, blood, bone marrow, kidney and the liver. Although a number of sulfonamides have been reported to have produced hepatic lesions, hepatitis following therapy with trimethoprim-sulfamethoxazole is a rather rare event. While trimethoprim has not yet been reported as a cause of hepatic disorders, sulfamethoxazole has occasionally been described as inducing hepatic injury. In some cases, these reactions are accompanied by symptoms indicative for allergic reactions such as fever, rash and eosinophilia. Seven well documented cases are analyzed and discussed with respect to the nature of side effects caused by co-trimoxazole.