Endothelin-1 (10(-11)M-10(-7)M) was incubated with human umbilical vein endothelial cells and cells derived from amnion and decidua and prostaglandin production was determined. The rates of biosynthesis of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and prostaglandin E2 (PGE2) by endothelial cells were increased significantly by treatment with endothelin-1. Amnion cell PGE2 production was reduced significantly by endothelin-1 treatment whereas decidual PGE2 and prostaglandin F2 alpha production was unaffected by this treatment. Thus, it is possible that endothelins may play a part in the regulation of uteroplacental hemodynamics and the mechanisms of parturition.