The present paper studies the neuronal pathways connecting the optic tectum(?)the nucleus profundus mesencephali(NPM)and the nucleus isthmi,and the morph-ology of their originating cells in Gekko gekko and Shinisaurus crocodilurus byusing horseradish peroxidase(HRP)tracing method.The results indicate that 1.There exist reciprocal topographic projections between the tectum and the nucleus.isthmi pars magnocellularis(Imc);2.The ipsilateral tecto-Imc projection originatesfrom cells mainly located in layer 7,which have piriform somata with radical den- drites;the ipsilateral Imc-tectal projection originates from piriform or polygonalneurons with a small dendritic field;3.Cells labeled in NPM following tectal injections are fusiform in shape,paler in color,whereas NPM cells labeled followingisthmic injections are numerous,whose thick dendrites often go up to the tectum(?)4.NPM injections label both tectal and isthmic cells.The former are mainly loca-ted within layer 7,while the latter are in Imc and Ipc.