The authors describe the operational features and performance characteristics of a new commercial kit designed to measure the amount and functionality of amniotic fluid surfactant. This kit, the Lumadex-FSI Test, is based upon the manual foam stability index test. The test requires no more than 3.0 ml of centrifuged amniotic fluid. Initial experience based on 172 specimens, including 19 cases of neonatal respiratory distress syndrome (RDS), revealed the Lumadex-FSI Test to have excellent discriminating ability in predicting the likelihood of RDS. In 18 of 19 cases in which RDS was noted, the foam stability index was 46 or less. A foam stability index of 47 or above was associated in 133 of 134 cases with fetal pulmonary maturity. Based upon contamination studies with maternal serum and meconium, the authors observed that a 1% contamination with blood, or 4% contamination with meconium, would artifactually increase the Lumadex-FSI value. The Lumadex-FSI Test demonstrated a clinical reliability similar to that of the manual foam stability index procedure, in addition to making the test simpler, faster, and more accessible to the clinician, in whose hands this test will have unique input into the management of high-risk pregnancies.