IN the normal retinotectal topography established during the embryonic development of the chick visual system, retinal ganglion cell axons from the nasal retina connect to the posterior part and temporal retinal axons connect to the anterior part of the optic tectum. For the investigation of position-specific gene expression along the nasal-temporal axis of the retinal neuroepithelium (RN), differential display PCR was carried out from the nasal or temporal part of the RN at HH11 (E2). We found several genes that are differentially expressed either in the nasal or in the temporal part of the RN and the analysis of the asymmetrically expressed fragments showed at least one cDNA fragment to be exclusively expressed in the nasal RN. This fragment was 550 bp in size.