Nosocomial Respiratory Syncytial Virus infections are frequently reported and tend to be more severe, because of comorbidity, such reports, however, are frequently from a single centre. The incidence and outcomes of nosocomial Respiratory Syncytial Virus infection in UK neonatal units over a five year period were estimated by interrogating the Capse Health Care Knowledge Systems database, which contains anonymised details of 55% of UK hospital admissions. A total of 79,642 admissions commenced on the infants' date of birth and contained an ICD-10 code for low birth weight or immaturity. Thirty-seven of the 79,642 admissions also contained a Respiratory Syncytial Virus code. Two (5.4%) with Respiratory Syncytial Virus and 2,736 (3.4%) without Respiratory Syncytial Virus died. Survivors with Respiratory Syncytial Virus codes experienced significantly increased length of stay. In the extreme immaturity sub-group the length of stay was 117.5 days with Respiratory Syncytial Virus and 51.3 days without Respiratory Syncytial Virus (p = 0.0002). In the low birth weight or other preterm sub-group the length of stay with Respiratory Syncytial Virus was 69.2 and without Respiratory Syncytial Virus 14.7 days (p < 0.0001). The observed low rate for nosocomial Respiratory Syncytial Virus (0.46/1000 admissions) should be regarded as a minimum. The increased length of stay in infants with Respiratory Syncytial Virus infection emphasises that units should have guidelines to prevent and deal with Respiratory Syncytial Virus outbreaks.