In most cases erythema multiforme runs a mild course free from alarming symptoms. Nevertheless, cases of severe forms of this disease have occasionally been reported. Severe erythema multiforme differs from the common form in the following ways: High fever and severe constitutional symptoms are present; the cutaneous eruption is more extensive, with vesicular and bullous lesions predominating, and there is severe involvement of the mucous membranes. Erythema multiforme with severe and predominant involvement of the mucous membranes has in the past often not been recognized as erythema multiforme and therefore cases have been reported under names such as ``ectodermose érosive pluriorificielle'' (Rendu1and Fiessinger2), ``dermatostomatitis'' (Baader3) and"eruptive fever with stomatitis and ophthalmia''(Stevens and Johnson4). In this communication the course and manifestations of severe erythema multiforme will be discussed and 2 cases which were recently observed at the Massachusetts General