The aim of this study is to determine if endothelin levels are elevated in women with preeclampsia and eclampsia and if these levels correlate with other laboratory features of disease severity. Methods: Endothelin levels were measured by means of enzyme-linked immunosorbent assay in the plasma of 12 pregnant women with eclampsia and 20 with preeclampsia and in the plasma of 22 control pregnant women. At the same time, routine laboratory tests for eclampsia and preeclampsia, such as uric acid, creatinine, and urine protein levels, were obtained. The mean levels in the different groups were subjected to statistical analysis with the analysis of variance. Results: Endothelin levels were elevated in women with eclampsia (4.9 ± 3.2 fmol/ml) and preeclampsia (3.7 ± 1.9 fmol/ml) as compared with those of control pregnant women (1.4 ± 0.5, P < 0.001). Endothelin levels were correlated positively with serum levels of uric acid (P < 0.05) and with diastolic blood pressure (P < 0.04) in the eclamptic group. Conclusions: We conclude that the increased endothelin-1 production may play a role in the pathogenesis of eclampsia and preeclampsia and correlate with the severity of these conditions.