The objective of this study was to evaluate the effect of increased circulating endothelin on fetal and placental growth in the rat. Indwelling arterial and venous catheters were placed on day 14 of a 22-day gestation in timed-pregnant Sprague-Dawley rats. Saline, 0.2 nmol/kg/h endothelin, or 0.5 nmol/kg/h endothelin was continuously infused from day 15 through 21 in randomly assigned animals (n = 12 in each group). Maternal arterial blood pressure and serum endothelin levels were evaluated on days 15, 18, and 21 of gestation. On day 21, pregnancy outcome data including fetal and placental weights, litter size, and the occurrence of stillbirths were ascertained, and fetal blood was obtained for serum endothelin levels. All data were compared among the three groups, and statistical significance was determined by analysis of variance. Endothelin infusion resulted in a dose-dependent decrease in fetal and placental weights when compared to saline-treated pregnancies. A significant increase in maternal arterial blood pressure was noted only in the 0.5 nmol/kg/h endothelin group. Fetal and placental growth restriction occurred in the absence of maternal hypertension in the 0.2 nmol/kg/h group. These results demonstrate that endothelin infusion causes restriction of fetal and placental growth, even in the absence of maternal hypertension.