We undertook a study of infection with Epstein-Barr virus (EBV) in order to ascertain the spectrum of complications from this disease. During a 6-year period, 51 children were admitted; review of the 50 available records confirmed the diagnosis of EBV infection in 48, 37 of whom had clinical infectious mononucleosis. The indications for admission were diagnostic evaluation in 14 (29%) children, airway obstruction in 12 (25%) children, dysphagia and dehydration in 11 (23%) children, airway obstruction and dehydration in 2 (4%) children, severe malaise in 2 (4%) children, pneumonia in 2 (4%) children, encephalitis in 2 (4%) children, Guillain-Barré syndrome in 1 (2%) child and unrelated conditions in 2 (4%) children. Additional complications developing during hospitalization included peritonsillar abscess, pancytopenia, pleural effusion, hepatitis and hyponatremia. We believe that infection with EBV has a higher morbidity in childhood than previously appreciated.