The objective of this study was to determine how the neonatal mortality rate has changed since surfactant (S) therapy was introduced in our Neonatal Intensive Care Unit (NICU), and to evaluate the efficacy of surfactant therapy in respiratory distress syndrome (RDS) patients. Incidences of risk babies such as outborns, prematurity, low birth weight infants and RDS, and neonatal mortality rates were compared between 'pre' (control, 1988 to 1991, n=4,861) and 'post' S period (study, 1993 to 1996, n=5,430). In RDS patients of 'post' S period, neonatal mortality rate was compared between S-treated and non-treated patients, and chest X-ray and ventilatory parameters were compared between pre- and post-72 hr of surfactant treatment. Surfactant therapy showed short term effects, judging by the decrease of early neonatal deaths and improvement of chest X-ray and ventilatory parameters in RDS patients. The overall neonatal mortality rate had a tendency to decrease in spite of increased incidences of risk babies in 'post' S period but it was less than expected. The reasons were thought to be that we had a high proportion of risk babies, and there was some bias in patient selection for surfactant therapy and its use. In conclusion, with the active prevention of risk baby delivery and appropriate use of surfactant, better results could be expected.