This study examined the mechanism of wound repair in the early chick amnion following surgical puncture. The chick amnion is a bilayered membrane with ultrastructural features similar to the human amnion, and thus may provide a model of the consequences of amnion puncture following first trimester amniocentesis in humans. Chick amnion was wounded on day 4-5 of incubation. The rate of wounding was measured as 40 microm2/minute by hourly measurements of wound area from initial wounding to a point where the wound appeared to be fully closed. Morphological changes were examined by scanning electron microscopy of amniotic membranes with the overlying chorionic membrane removed. Cells bordering the wound arranged themselves circumferentially during the healing period and eventually came together as a cellular pile up as the healing process was complete. The presence of an actin cable was revealed by fluorescein isothiocyanate-labeled phalloidin. The actin was circumferentially arranged around the wound margin and appeared within 10 minutes after wounding. Treatment of the amnion with the inhibitor of endogenous Rho, C3 exotransferase, inhibited actin cable formation, suggesting that formation of an actin cable within the amnion during wound healing is Rho dependent.