We analyzed the data from the ICST to assess the effectiveness of prophylactic surfactant for treatment of hyaline membrane disease compared to any other treatment in patients with birthweights of 501-1250 gms and gestational age <30 wks. The study population consisted of all patients admitted to the participating nurseries during the study period who met these birthweight and gestational age criteria. We excluded patients with congenital anomalies and patients who were admitted after 48 hrs of age. 12 of the 13 ICST centers participated; six used prophylactic surfactant preferentially and six almost never used prophylactic surfactant. We studied 1097 patients of whom 381 received prophylactic surfactant. All analyses controlled for birthweight and study center. Overall, we found that survival was significantly increased in the prophylactic surfactant patients (84% vs 72%, p<0.05). In addition, survival without supplemental oxygen at 36 wks postconceptional age was also increased in prophylactic surfactant patients(60% vs 46%, p<.05). Although the results were heavily influenced by the fact that nearly all of the patients treated with prophylactic surfactant came from only 6 of the 12 centers, these data support the conclusion that using or being predisposed to use prophylactic surfactant resulted in improved survival in patients at risk for developing hyaline membrane disease. This research was supported, in part, by funds from ONY, Inc and Forest Labs.