Background. We use nasal-CPAP and surfactant routinely in babies with a/A PO2 <0.22. This treatment reduces the severity of RDS. Nevertheless, some babies need mechanical ventilation later on .Material & Methods. 60 babies (GA <30 wk, age 2-72 h, a/A PO2 <0.36) with RDS in progression were randomized to treatment with Curosurf (200 mg/kg) either immediately (“early”) or at a/A PO2 <0.22 (“late”). Failures: mechanical ventilation(a/A PO2 <0.15 or severe apnea) during 7 d. Results. There were no significant differences between groups at entry. GA 27.3 wk, BW 1000 g, mean. 21% early treated failed vs. 67% late, p = 0.001. Fisher's two-tailed. Mortality 9.1% vs. 30%, p = 0.05. Other complications of RDS were rare. Conclusion. “Early” Curosurf during nasal-CPAP is highly effective in RDS and GA <30 wk.