Measles pneumonitis, as well as encephalitis, is the most important complication associated with mortality in measles. Many medications including steroids and vitamin A have been applied to pediatric measles pneumonitis. However, the efficacy of such medication has not yet been established. This study is aimed at evaluating the effectiveness of surfactant replacement therapy in pediatric measles pneumonitis. Five patients (aged 1-2 years) with measles pneumonitis were transferred to our emergency center. On the transferred day, Surfactant-TA was administered by intratracheal method. After administration of surfactant, PaO2/FIO2 increased from 63.6 +/- 11.0 (mean +/- SE) to 206.2 +/- 54.1 in an hour and to 163.8 +/- 34.8 in 24. At the same time, the CO2 elimination and the dynamic compliance were improved. Because of these effects, the peak inspiratory pressure employed in mechanical ventilation could be reduced. It is concluded that surfactant replacement therapy can prevent the patients with measles pneumonitis from hypoxemia and ventilation-induced lung injury. However, further study is needed to maintain the improved oxygenation. Recently, it is reported that the effect of exogenous surfactant on oxygenation and activity of pulmonary neutrophils is regulated by the amount and/or concentration of administered surfactant. Therefore, it is an urgent issue to find out the optimum amount and concentration of exogenous surfactant used clinically.