A rapid simple economical test has been devised to determine whether pulmonary surfactant is present in amniotic fluid. Analysis of 50 samples of the amniotic fluid by the foam test which showed that three zone infants of 6 of 6 patients with clearly negative tests had severe respiratory distress syndrome or transitional respiratory distress whereas those of 29 of 29 patients with clearly positive tests were free of respiratory distress. In 15 cases with intermediate tests 8 of the infants showed mild to severe respiratory difficulty. The test has high predictive value for RDS when applied to uncontaminated amniotic fluid.