Replacement therapy with surfactant extracts in premature infants with respiratory distress syndrome has been evaluated in several clinical trials. The results of individual trials do not provide conclusive evidence that administration of a single dose of surfactant improves morbidity or mortality. Meta-analysis is a statistical method to combine the results of such clinical trials, and combined analysis provides a means to overcome the problem of not being able to detect significant small differences in individual trials due to these small sample sizes. Seven clinical trials (277 patients treated with nonhuman surfactant extract and 263 controls) met the criteria for analysis; five outcome measurements (mortality, patent ductus arteriosus, pneumothorax, intraventricular hemorrhage, and bronchopulmonary dysplasia) were selected to estimate the treatment effect. The meta-analysis showed that a single dose of surfactant administered before the first breath or within 15 hours of birth significantly decreased the mortality rate (95% confidence interval = -0.19 to -0.03) and the risk of developing pneumothorax (95% confidence interval = -0.28 to 0.14) in infants with respiratory distress syndrome. Further clinical trials are needed to evaluate other aspects of surfactant replacement therapy in premature infants because inconsistent results were observed among the seven analyzed studies.