Amniotic fluid L/S ratios were determined in 78 patients. No infant delivered within 48 hours after a mature ratio was recorded developed respiratory distress syndrome (RDS). Two of 8 babies born after the L/S ratio indicated immaturity developed RDS. Discrepancies between amnotic fluid creatinine and fetal weight were noted. The test was found to be very helpful in the management of high-risk pregnancies and in repeat cesarean sections.