Endothelin is a potent vasoconstrictor released from injured endothelial cells. As the pathophysiology of the mechanisms of Preeclamptic toxaemia are not exactly Known, the present study aimed at determining the level of Endothelin in normal & preeclamptic pregnant women. The study also aimed to postulate any possible relation between the severity of the Preeclamptic toxaemia & the levels of circulating Endothelin-1 (ET -1). The study was carried out on 45 pregnant women at 37 - 40 weeks of gestation. They were classified into 3 groups, each 15 patients, namely; Control group (normal Pregnancy), Group of pregnant women with mild Preeclamptic toxaemia, and a third group of women with severe Pre-eclamptic toxaemia. The results showed significant increase in the systolic and diastolic pressure & ET-1 levels in mild & severe Pre-eclamptic toxaemia, compared with control group (p