Primordia of the retina and the tectum of different ages (13 to 20 embryonic days) were transplanted as single or double grafts into the anterior chamber of the eye of normal syngeneic adult rats (Fischer 344). After 2-37 weeks (mostly 4-16 weeks), host rats were sacrificed and their eyeballs were dissected, frozen and sliced to 10 microns thickness and examined histologically by using Nissl and acetylcholinesterase (AChE) stains. Survival of the retinal single grafts, the tectal single grafts and the double grafts of both tissues were 21.7% (5/23), 41.2% (14/34) and 73.9% (17/23), respectively. The single grafts of the retina surviving on the iris of the host anterior chamber were observed through the transparent cornea as an irregular, translucent and whitish masses, inside of which small blood vessels were seen to enter. The grafted tissues contained many darkly stained cells and formed tubular structures of varying sizes and in part exhibited rosette-like structures. The surviving single grafts of the tectum grew forming round, developing tissue on the host iris. The surface of the graft was smooth and vascularized. In Nissl sections, grafts contained large cells densely distributed, in particular in the center of the solid tissues. Areas of strong AChE-positive reaction in the graft were located close to the host iris. Double grafts of the retina and the tectum were observed on the host iris to fuse about 2 weeks after transplantation. On Nissl sections, the retinal part of the grafts of about 2 weeks (short term) of survival demonstrated rosette formation of two (i.e., inner and outer) layers composed of light and dark cells, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)