Respiratory syncytial virus (RSV) is isolated in 15-25% of young Malaysian children with bronchiolitis.',2 Although this observation is consistent with experience reported in other developing nations in the tropics,3•4 it is lower than that of temperate developed nations where RSV is isolated in 60 - 80% of young children with viral bronchiolitis.5,6 The majority of infections are mild, easily cared for at home and only 1% of children with RSV bronchiolitis require in-hospital care.' However, several categories of children have been identified to develop severe RSV bronchiolitis that is asso-ciated with an increased risk of mortality and significant morbidity. This 'high-risk' group includes children who are very young, ex-premature (gestation less than 36 weeks), children with chronic lung disease, congenital heart disease and immunodeficiency, namely, haematological transplant recipients.8'9 It is for this category of children in whom effective therapeutic strategies for the treatment of RSV bronchiolitis are most important.