A 27-year-old American white woman was admitted to our dept. on July 29, 1972, complaining of enlargement of lymph-nodes on both sides of the neck, general malaise, swallowing difficulty and high fever(39℃). The diagnosis was made on the basis of the titer of heterophile antibody, lymphocytosis and atypical lymphocytes on the blood smear and the clinical signs. Review of literatures as for Infectious Mononucleosis was also attempted briefly.