Respiratory viruses are the most common infections in healthy children. The impact of these infections in cancer patients has been only recently recognized in Chile. Aim: To establish the frequency and epidemiological-clinical profile of respiratory virus infections in children younger than 15 years of age with acute lymphoblastic leukemia requiring hospitalization due to a febrile neutropenic episode. Methods: All children < 15 years of age requiring hospitalization in the Regional Hospital of Valdivia, Chile, with cancer, fever and neutropenia between November 1 2002 and October 31 2004 were studied. Nasopharygeal aspirate were obtained and tested by direct immunofluorescent assays for influenza A-B virus, parainfluenza virus type 1, 2, 3, respiratory syncytial virus (RSV) and adenovirus. Results: Respiratory viruses were detected in 25% of 44 febrile neutropenia episodes occurring in 25 patients. Viruses detected were, influenza (3/11), parainfluenza (3/11) RSV (2/11), adenovirus (1/11), parainfluenza + RSV (1/11), and parainfluenza + adenovirus (1/11). Four (36%) of cases were nosocomial. Respiratory symptoms were present in 9 children, seven of whom had inferior respiratory tract symptoms. One patient died of persistent RSV infection, agranulocytosis and extensive bilateral pneumonia. Conclusions: Respiratory viruses were detected in 25% of febrile neutropenic episodes in children with ALL. This high detection rate together with the frequent involvement of the lower respiratory tract and the possibility of death strongly favors the inclusion of respiratory virus diagnostic tests in the evaluation of these children during autumn and winter season