Respiratory syncytial virus (RSV) causes serious respiratory illness in preterm children with bronchopulmonary dysplasia. In a prospective randomized placebo-controlled trial, 21 children received one dose of PFP-2 (purified fusion [F] protein) vaccine or influenza vaccine (placebo). Children were followed for adverse reactions and RSV illness over two respiratory seasons. Sera were obtained for determination of IgG titers to RSV F protein and neutralizing antibody titers before and 1, 6, and 12 months after vaccination. Adverse reactions were few. Four-fold F protein rises occurred in 9 of 10 PFP-2 and 0 of 11 placebo recipients. Six PFP-2 recipients had low prevaccination neutralizing antibody titers (< 1:450); all had 4-fold rises. By 12 months, F protein and neutralizing antibody titers in all 21 children were similar. RSV illness occurred in 6 of 11 placebo versus 1 of 10 PFP-2 recipients (P = .06); 1 placebo child required hospitalization. PFP-2 vaccine appears safe and immunogenic and may protect children with bronchopulmonary dysplasia against serious RSV disease on reinfection.