Within a model cohort of 1,000 preterm infants of less than 30 weeks of gestation, the incidence and mortality of RDS change if corticosteroids are used prenatally and surfactant prophylactically or therapeutically after birth. Combined pre- and postnatal therapies give the best results: approximately 125 extra survivors. Therapeutic surfactant administration even in combination with prenatal corticosteroids has cost implications because extra intensive care beds (7-11%) are needed. More special care places (12-24%) are required after each type of intervention. The estimated costs per extra survivor are the lowest for prenatal corticosteroid administration. The combination of corticosteroids prenatally and prophylactic surfactant postnatally seems to be most cost-effective because it produces the greatest number of survivors and the lowest number of intensive and high dependency care days in hospital.