Cortisol and cortisone were estimated in ten samples of amniotic fluid from normal mothers at term, and in five samples from diabetic mothers taken at 36–38 weeks during artificial induction or at Caesarean section. The steroids were estimated by a chromatographic procedure via their acetates. Small but definite quantities of both steroids were found in all the samples examined. The concentration of cortisol was 2.6 ± 0.32 μg/100 ml in the normal fluids, and 2.2 ± 0.37 μg/100 ml in the diabetics' fluids. The concentration of cortisone was 1.3 ± 0.14 μg/100 ml in normal, and 1.4 ± 0.19 μg/100 ml in the diabetics' fluids. The differences between the normal and diabetics' fluids were not significant. Contrary to some previous work it is concluded that small quantities of these steroids are regularly present in normal amniotic fluid. The possible role of these steroids in the aetiology of foetal abnormality in diabetic pregnancy is discussed.