Mechanical stretching increases synthesis and release of prostaglandin E2 (PGE2) in cultured amnion cells. The maximum level of PGE2 in stretched amnion cells is three times higher than that in nonstretched amnion cells. The maximum level of PGE2 in stretched cell medium is nine times higher than the maximal level of PGE2 in nonstretched cell medium. 3H-thymidine incorporation into DNA is 211 ± 25 cpm/105 cells in nonstretched groups; that in stretched groups is 582 ± 94 cpm/105 cells. There is a significant difference between the two groups. These results suggest that stretch stimulation facilitates prostaglandin production in fetal membranes, which may contribute to uterine contraction in labor.