Samples of amniotic fluid from 514 non-diabetic and 69 diabetic patients were analyzed for phospholipid content. Results were correlated with incidence of respiratory distress syndrome (RDS) in the neonate. The incidence of RDS was 4.5% among diabetics and 5.3% among non-diabetics. In the presence of phosphatidylglycerol (PG), no infant developed RDS while in the absence of PG the incidence of RDS was 16.7% and 14.4%, respectively. In the presence of a mature lecithin/sphingomyelin (L/S) ratio the respective incidence of RDS was 1.6 and 1.8, while with an immature L/S ratio the incidence of RDS was 28.6% and 29%. The incidence of RDS after 37 weeks gestation was 0% among diabetics and 0.6% among non-diabetics. We conclude that amniotic fluid phospholipids are equally predictive of risk for RDS in diabetics as among non-diabetic patients. We suggest that in patients with accurate gestational dating, amniotic fluid analysis for phospholipids might not be necessary to establish fetal lung maturity.