Severe acute respiratory syndrome (SARS), a new contagious respiratory disease associated with a novel coronavirus, has spread worldwide and become a global health concern after its first outbreak in Guangdong Province of the People's Republic of China in November 2002. The clinical presentation and the radiologic, hematologic, biochemical, and microbiologic findings of a 56-day-old male infant with SARS are described. Some clinical and laboratory features are similar to those reported in adult and pediatric patients. However, this infant had a more severe clinical course as compared with the older children. This is the youngest patient with symptomatic SARS reported to date.