The results obtained with porcine surfactant (Curosurf) administration for the treatment of hyaline membrane disease (HMD) are reported. Thirty premature infants weighing 700 to 2,000 g with severe HMD (mechanical ventilation and oxygen requirement (FiO2) greater than 60% were randomly allocated at 2 to 15 hours postnatal age. Eight of the 30 patients included in this group participated in a multicenter european trial. The fifteen infants with mean gestational age (GA) of 29.5 weeks included in the treatment group (T), were treated at 8.6 hours of life with a single dose of 200 mg/kg Curosurf given intratracheally while 15 infants of mean GA 30 weeks formed the control group (C). Infants in the T group showed an immediate, dramatic and sustained improvement of oxygenation as reflected by increased PaO2/FiO2 and arterial to alveolar PO2 ratios within 1 hour. This significant improvement in favor of T group (p less than 0.005) persisted for 2 days when control infants began to recover. This improvement in oxygenation allowed a significant decrease of FiO2 (p less than 0.005) and mean airway pressure (p less than 0.01) in the T group within 1 hour and up till the second day. Despite this early improvement obtained with Curosurf the survival rate at 28 days of life and the incidence of associated HMD complications were not significantly modified. However the tendency was towards decreased respiratory morbidity. The discussion will consider the value of multiple doses.