The appearance of severe acute respiratory syndrome (SARS) as a new clinical entity in 2003 has raised concerns among physicians about distinguishing it from more common respiratory infections such as influenza. This report from Taiwan compares clinical features of laboratory-confirmed SARS with those of culture-confirmed influenza in children and adolescents. There was a similar prevalence of fever, cough, chills, myalgia, and diarrhea between the 2 groups. However, patients with SARS were much less likely to have rhinorrhea, sputum production, and sore throat than were patients with influenza. While patients had similar frequency of leucopenia or lymphopenia, one third of patients with SARS had monocytopenia compared with none of the patients with influenza. Only 1 patient with SARS required mechanical ventilation, and all survived.