The seasonal problem of respiratory infections in children caused by respiratory syncytial virus (RSV) is worldwide. A number of these infections are known to occur by nosocomial acquisition. In order to reduce the risk, measures, such as cohort nursing and handwashing, have been used in the paediatric department of Odense University Hospital for three years. In a retrospective evaluation of this routine practice the incidence of nosocomial RSV infections was recorded. The overall rate of nosocomial infection was low, but was proportionally highest in the unit for children aged under 6 months; no change in incidence was seen over the three-year period. In the infectious disease unit, where the majority of RSV infected children were admitted, the rate of nosocomial infection decreased despite an unchanged routine. This difference cannot be explained simply on the basis of longer hospital admission of the children under 6 months of age, but might relate to acquired immunity in children of all ages in the infectious diseases unit or better facilities for segregation within that unit.