Despite the development of artificial surfactant and advances in respiratory support, respiratory distress syndrome (RDS) remains a major clinical concern. The relatively low prevalence of RDS requires test methods with very high diagnostic sensitivity and specificity for fetal lung maturity (FLM). Such methods often require sophisticated instrumentation, skilled staff, and long analytic times. This practice parameter discusses the usefulness of widely available methods and reaches several conclusions: (1) A satisfactory specimen of amniotic fluid is essential for effective laboratory assessment of FLM. (2) No test is immune from analytic interferences. (3) The lecithin/sphingomyelin (L/S) ratio or phosphatidylglycerol (PG) by thin-layer chromatography are unnecessary as obligatory panel components. (4) Either fluorescence polarization or lamellar body number density is an acceptable initial screening test. If maturity is indicated, no further testing is generally necessary. (5) If the result of the initial test in no. 4 is below but near the maturity criterion, the second rapid test usually can offer resolution; if the result is still immature, a third rapid test can be added (PG by Amniostat-FLM). (6) In the setting of poorly controlled diabetes, PG assessment by Amniostat-FLM should be performed to rule out false maturity predictions by the other rapid tests. Nevertheless, RDS will not develop in most fetuses in whom PG is not detected. (7) Clinical judgment remains the single most important criterion for fetal delivery.