Thirty preterm infants weighing > or = 800 g with clinical and radiological evidence of respiratory distress syndrome (RDS) requiring mechanical ventilation with FiO2 of > or = 40% were given modified bovine surfactant (Survanta). They were compared with equal number of historical controls. Infants who received surfactant showed prompt and highly significant improvement in FiO2, mean airway pressure, arterial/alveolar oxygen tension ratio and ventilatory index. There was significant improvement in mortality rate (10% vs 33%; p = 0.03). Among the survivors, surfactant-treated infants required shorter duration of continuous positive airway pressure (CPAP) (3.4 vs 9.6 days; p = 0.04). For survivors with birthweight of > 1000 g, surfactant-treated infants required shorter duration of ventilatory support (intermittent positive pressure ventilation + CPAP) (7.5 vs 18.9 days, p = 0.02). Overall, surfactant-treated infants achieved full enteral feeds sooner (15.7 days vs 24.6 days; p = 0.03) and required shorter duration of total parenteral nutrition (13.9 days vs 25.6 days; p = 0.02). We concluded that surfactant replacement therapy was effective in the treatment of preterm infants with RDS.