Respiratory syncytial virus (RSV) is a cause of serious respiratory infections in pediatric patients. RSV infection may be especially devastating in pediatric bone marrow transplant (BMT) recipients. Because of the high mortality attributed to RSV lower respiratory tract infection, a pilot study of preemptive treatment of asymptomatic RSV shedding in pediatric BMT recipients was conducted. Nasopharyngeal wash specimens from 25 pediatric BMT recipients were screened for RSV infection prior to patients' admission to the University of Utah Pediatric Bone Marrow Transplant Unit and then on a weekly basis during the 1996 and 1997 RSV seasons. Samples from 7 asymptomatic patients tested positive for RSV, and the patients were treated with aerosolized ribavirin for 5 days; none developed clinical RSV disease. Two patients had multiple episodes asymptomatic RSV shedding. One patient required 2 courses of treatment for clearance of RSV.