The superior brachial region of the left optic tract was lesioned in adult rats and foetal tectal tissue was implanted into the lesion site. The retinal projection from the contralateral (right) eye was examined 2 to 8 months later. In the majority of animals, retinal ganglion cell (rgc) axons were found to regenerate through cellular membranes which formed over the lesion. Axon growth could extend for up to 5 or 6 mm. Surviving tectal grafts were identified in all host rats. In animals in which regrowing rgc axons contacted tectal grafts, axons were found to innervate selectively their appropriate target regions within the graft neuropil.