Objective: To evaluate the efficacy and safety of two natural surfactants (curosurf and calsurf) on the treatment of preterm infants respiratory distress syndrome(RDS). Methods:From January 2007 to July 2009, we conducted a trial at the neonatal intensive care unit of Nanjing Children’s Hospital. Eighty-one premature babies suffered from RDS and requiring mechanical ventilation(MV)were recruited and divided into two groups:54 in curosurf group and 27 in calsurf group. The surfactant was administered by endotracheal intubation. Blood gas index,ventilator parameters,oxygenation index(OI),the duration of ventilator dependence and hours of oxygen requirement,time in hospital and incidence of complications before and after surfactant administration were analyzed and compared. Results:The oxygenization and ventilator parameters of the two groups showed significant improvements at 24h after administration in comparison with those before surfactant therapy(both P<0.05). There were no statistical differences in the duration of MV or oxygenation,hospitalization time. No statistically significant differences were found in incidence of mortality or complications,which included retinopathy(ROP)and necrotizing enterocolitis(NEC),pneumonorrhagia,pneumatothorax,patent ductus arteriosus (PDA). Both groups had sustained decreasing mean airway pressure(MAP)and OI after surfactant therapy,but time-effect curves were different. MAP and OI of curosurf group decreased most significantly within the initial 4 hours after administration (P < 0.01)compared to the calsurf group,which mainly decreased between the 4th hour and the 8th hour after administration(P < 0.05). Conclusion:In the treatment of preterm infants with RDS,the efficacy and safety of curosurf and calsurf were similar,while curosurf works earlier than calsurf. We should adjust the MV parameters properly in accordance with the different time-effect curves of the two surfactants,so as to reduce complications.