Wound closure in the ectoderm of Xenopus early neurulae and chick primitive-streak embryos has been studied by scanning electron microscopy (SEM). Initial gaping of the wound and a cobble-stone appearance of cells peripheral to the wound in both Xenopus and chick confirm that the ectoderm is under lateral tension at these stages. Healing is rapid: in Xenopus embryos wound closure has started within 5 min of wounding; in chick healing is almost complete within 30 min in some cases. The SEM observations suggest that in Xenopus embryos changes in cell shape are the major mechanism for wound closure. In chick embryos wound healing is also accompanied by changes in the shape of the marginal cells, but evidence is presented that in this system cell proliferation is important. The mechanisms of wound healing in Xenopus and chick embryonic ectoderm are compared with those of wound healing in other tissues.