Cultured amnion, choriodecidua and intact fetal membrane produced similar quantities of prostaglandin E2 (PGE2) (1-5 ng/ml). Choriodecidua and intact fetal membrane also produced very high levels of PGE2 metabolites (100-1000 ng/ml). The total production of PGE (PGE2 + PGE2 metabolites) was similar in intact fetal membrane and in choriodecidua, suggesting that the amnion, although a source of PGE2, contributes little to the overall PGE production by fetal membranes.