This prospective study was designed to assess pulmonary function (functional residual capacity, FRC; dynamic lung compliance, CLdyn; and total pulmonary resistance, RL) at 1 year of corrected age in infants with neonatal respiratory distress syndrome treated with natural porcine surfactant (Curosurf) (n = 13), as compared to nontreated control infants (n = 9). Values from 21 healthy infants of similar age served as reference. We found similar pulmonary dysfunction (decreased CLdyn, elevated RL) in both patient groups. These results suggest that surfactant replacement therapy does not affect pulmonary function at 1 year of age in infants who survive respiratory distress syndrome.