Aim: Rescue surfactant trial is rational for other causes of neonatal respiratory insufficiency. Hypothesis: Surfactant dysfunction is involved also into the development of Non-RDS neonatal respiratory disorders. Settings: Prospective clinical cohort study in a tertiary neonatal service. Patients: 149 artificially ventilated newborn infants, classification of the respiratory diseases according to Hjalmarson for RDS N=70, wet lung N=17, pneumonia N=23, for congenital diaphragmatic hernia CDH N=6, for non immunologic hydrops fetalis NIHF N=6. 27 ventilated lung healthy infants with a postnatal surgical intervention served as controls. Measurements: Determination of quotient of palmitic acid to stearic acid (P/S-ratio; gas chromatography) and quotient of lecithin to sphingomyelin (L/S-ratio; HPLC), minimal surface tension (γ-min) by pulsating bubble surfactometer. Data and tracheal fluid were collected during the first 24 hours after entering the study. Results: 1. In tracheal effluent of infants with RDS there is a low content of phospholipids and high surface tension. 2. About 50% of infants with connatal pneumonia show low content of phospholipids and high surface tension in tracheal fluid. 3. In infants with wet lung. CDH and NIHF there were no definite signs of surfactant deficiency and/or disturbed surfactant function. 4. In tracheal fluid of some infants with respiratory insufficiency we found both a high phospholipid content and high surface tension pointing to impaired surfactant function. Conclusion: The surfactant system is depleted in only one third of ventilated Non-RDS newborn infants. In these infants surfactant treatment is indicated if surfactant deficiency or dysfunction is clearly evident by analysis of tracheal fluid.