Many investigators have examined the retinotectal projection following regeneration, but the mapping technique used in these studies mainly involved recording action potentials from presynaptic terminals. Hence it was not possible to analyse the postsynaptic phenomena underlying the target finding process of the retinal fibers. In the present study, the process of making functional synapses was examined using field potentials generated by small spots of light fixed in the visual field. The results show that regenerating retinal fibers first make functional but temporary, unspecific and diffuse synapses before reaching the target area to form a sharpened retinotopic projection. It is suggested that the formation of synapses subserves an important role in the target finding process.