This prospective study evaluated the frequency and severity of respiratory symptoms during the second respiratory syncytial virus (RSV) season in an italian cohort of preterm infants (< or = 35 weeks) who had received palivizumab prophylaxis in their first year of life (October 2004-April 2005) and who had not previously been hospitalized for RSV-induced lower respiratory tract infection (LRTI). infants were evaluated at enrolment (May-September 2005), in October/November 2005 and in April 2006. The occurrence of any respiratory episode, the rate of hospitalization for respiratory-related LRTI, total length of stay in hospital, physician-documented recurrent wheezing (>or = 3 physician-documented episodes of wheezing) and use of airway medication/antibiotics were recorded during follow-up. All infants had prior palivizumab prophylaxis during their first RSV season. In the total evaluable population (n=260), 32.3% of infants experienced at least one respiratory episode, 3.8% required short hospitalization because of LRTI, 8.5% had physician-documented recurrent wheezing, and 48.8% required airway medications/antibiotics during follow-up. in this study the rate of airway morbidity, hospitalization and physician-documented recurrent wheezing during the second RSV season was low among preterm infants who had received prior palivizumab prophylaxis.