CLINICIANS may be led to consider a diagnosis of infectious mononucleosis when presented with a patient with an acute febrile illness and a rash. Textbooks, especially older ones, frequently state that eruptions are frequent and the literature quotes an incidence of from 3% to 100% of patients. The purpose of this paper is to place the cutaneous and mucocutaneous manifestations of infectious mononucleosis in a perspective that will be of some practical clinical value. Dr. Hoagland has collected data on approximately 300 cases of carefully documented infectious mononucleosis and has previously presented diagnostic criteria.1-6All patients were personally questioned and examined by him and most were hospitalized. In essence, criteria for diagnosis consisted of a compatible clinical syndrome—fever, lymphadenopathy, and sore throat—plus supportive laboratory evidence —relative and absolute lymphocytosis persisting at least 10 days and properly interpreted serologic tests. The heterophile test must be significantly positive and must persist