By use of wheat germ agglutinin (WGA) cDNA as a transgene, we have succeeded in generating a transgenic mouse line in which the visual pathways can be accurately and reproducibly visualized. The WGA transgene was expressed in the retinal rod bipolar cells under the control of mouse L7 promoter. The transgene product, WGA protein, was transferred from the bipolar cells to the amacrine cells and the ganglion cells across synapses in the retinal neural circuitry and further conveyed along the optic nerve to the visual centers such as the suprachiasmatic nucleus, the lateral geniculate nucleus, the pretectal nucleus and the superior colliculus. By crossing the WGA-expressing transgenic mice with the retinal degeneration mutant mice, we analyzed change in the visual pathways by monitoring WGA immunoreactivity and found that the disorganization process of the visual pathways was relatively slow in spite of the rapid degeneration of the photoreceptor cells. Thus, this transgenic mouse line would provide a useful tool for analyzing phenotypic changes in the visual pathways of various mutant mice.