Methods. We analyzed clinical and laboratory data on 13 patients who were <16 years old with SNV infection from 1993 through March 2000 identified from a database at the University of New Mexico.Results. The patients ranged from 10 to 16 years of age, with a median of 14. Fifty-four percent were female. Fifty-four percent were Native American. The most common prodromal symptoms were fever, headache, and cough or dyspnea (100%); nausea or vomiting (90%); and myalgia (80%). The most common physical findings at admission were tachypnea (67%) and fever (56%); hypotension was seen in 33% of patients. On admission, all patients manifested thrombocytopenia (median platelet count: 67 000/mm 3 ) and elevated lactate dehydrogenase (median level: 1243 IU/L), and >85% of patients had elevated levels of serum aspartate aminotransferase, alanine aminotransferase, and hypoalbuminemia. Leukocytosis and hemoconcentration were seen in less than one third of patients at admission. HCPS developed in 12 of the 13 patients (92%), and 4 of those 12 died (33% casefatality ratio). The majority of HCPS patients (8 of 12 [67%]) were critically ill and required mechanical ventilation. Extracorporeal membrane oxygenation was used in 2 patients, 1 of whom survived. An elevated prothrombin time (>14 seconds) at admission was predictive of mortality.Conclusions. Infection with SNV in children and adolescents causes HCPS with a clinical course and mortality rate similar to that described in adults. We believe that early recognition of HCPS in children and adolescents and appropriate referral to tertiary care centers that are experienced with HCPS are important in reducing mortality. Pediatrics 2001;108(2). URL: http://www. pediatrics.org/cgi/content/full/108/2/e27; hantavirus, children, adolescents, extracorporeal membrane oxygenation.