The central projections of the retinal ganglion cells of the cat were examined using the method of retrograde transport of horseradish peroxidase. Peroxidase was injected into the lateral geniculate nucleus and into the superior colliculus by means of a recording micropipette. After injections at retinotopically homologous points in these two structures in separate animals, tha patterns of retinal ganglion cell labeling were compared. We found that there were three populations of ganglion cells: small cells, that projected predominantly to the superior colliculus; medium-sized cells, that projected predominantly to the lateral geniculate nucleus; and large cells, some of which projected to both structures, and some of which projected to the lateral geniculate nucleus alons. Quantitative studies showed that the average size of the cells in each population was smaller at the area centralis than in the periphery. These results could be directly related to physiological classifications of retinal ganglion cells proposed by other authors.