SummaryDetection of phosphatidyl glycerol (PG) in amniotic fluid of complicated pregnancies is now a well accepted technique for determining fetal lung maturity. Previous methods reported have been technically difficult and can only be performed in specialised laboratories. We report a simple one dimensional thin layer chromato-graphic method using a stain that specifically identifies phosphatidyl. glycerol by its unique colour. The method is simple to perform, faster and more economical than two dimensional methods.In addition to its simplicity the method detects lower levels of PG than have been previously reported and may allow a better understanding of the development of surfactant.Phosphatidyl glycerol (PG) is a surface active phospholipid that is present in the amniotic fluid of mature pregnancies (Hallman et al., 1976; Bent et al., 1982; Whittle et al., 1982). The presence of PG has been shown to coincide with fetal lung maturity (Whittle et al., 1982) and when it is in detectable amounts, respiratory distress syndrome rarely occurs, despite low lecithin-sphingomyelin (US) ratios (Plauche et al., 1982; Whittle et al., 1983).PG estimations have been demonstrated to be more reliable than L/S ratios for the prediction of fetal lung maturity in diabetes mellitus. rhesus incompatibility and premature rupture of membranes. It has been recommended that both L/S ratio and PG estimation are measured in the management of high risk obstetric cases before preterm delivery is undertaken (Bustos et al., 1979; Hallman and Teramo, 1979; Cunningham et al., 1982; Whittle et al., 1982).The conventional practice is to measure PG using a two dimensional thin layer chromatography system (Whittle et al., 1981). We describe a simple and reliable one dimensional method that is suitable for routine use in hospital laboratories. The method provides a rapid quantitative measurement of PG concentration. A specific PG stain is used, thus eliminating possible confusion with other phospho-lipids or other impurities. The method conveniently allows the simultaneous testing of multiple samples and each may be performed in duplicate.