Background: Diminished lung function appears to be a risk factor for respirato ry syncytial virus (RSV) infection/bronchiolitis in term born infants. Aims: To determine if diminished lung function prior to neonatal unit discharge was assoc iated with subsequent symptomatic RSV lower respiratory tract infection (LRTI) a nd respiratory morbidity in prematurely born infants. Methods: Of 39 infants in a tertiary neonatal intensive care unit (median gestational age 28 weeks, range 23-31), 20 had bronchopulmonary dysplasia. Lung function (compliance and resist ance of the respiratory system(Crs and R rs) and functional residual capacity (F RC)) was measured on the neonatal unit at 36 weeks postmenstrual age (PMA). Foll owing neonatal unit discharge, nasopharyngeal aspirates were obtained on every o ccasion, at home or in hospital, an infant had an LRTI. RSV was identified by im munofluorescence and/or culture. Results: The 15 infants who suffered a symptoma tic RSV LRTI had a higher mean Rrs and suffered more wheeze at follow up than th e rest of the cohort. Regression analysis showed that a high Rrs was significant ly associated with a symptomatic RSV LRTI; significant factors for cough were a high Rrs and a symptomatic RSV LRTI, and for wheeze were a high Rrs. Conclusion: Prematurely born infants, who had a symptomatic RSV LRTI and/or respiratory mor bidity at follow up, had worse lung function prior to neonatal unit discharge. Background: Diminished lung function appears to be a risk factor for respirato ry syncytial virus (RSV) infection / bronchiolitis in term born infants. Aims: To determine if diminished lung function prior to neonatal unit discharge was assoc iated with subsequent symptomatic RSV lower respiratory tract (LRTI) a nd respiratory morbidity in prematurely born infants. Methods: Of 39 infants in a tertiary neonatal intensive care unit (median gestational age 28 weeks, range 23-31), 20 had bronchopulmonary dysplasia. Lung function (compliance and resist ance of the respiratory system (Crs and R rs) and functional residual capacity (F RC)) was measured on the neonatal unit at 36 weeks postmenstrual age (PMA). Foll owing neonatal unit discharge, nasopharyngeal aspirates were obtained on every o ccasion, at home or in hospital, an infant had an LRTI. RSV was identified by im munofluorescence and / or culture. Results: The 15 infants who suffered a symptoma tic RSV LRTI had a higher mean Rrs and suffered more wheeze at follow up than th e rest of the cohort. Regression analysis showed that a high Rrs was significant ly associated with a symptomatic RSV LRTI; significant factors for cough were a high Rrs and a symptomatic RSV LRTI, and for wheeze were a high Rrs. Conclusion: Prematurely born infants, who had a symptomatic RSV LRTI and / or respiratory morbidity at follow up, had worse lung function prior to neonatal unit discharge.