Retinal ganglion cells are a morphologically diverse group of neurons. They differ with regard to soma size, dendritic field extent, branching pattern of dendrites, level of dendritic arborization within the inner plexiform layer and site of axonal termination in subcortical nuclei. In spite of their diversity, many authors have found it possible to relegate individual ganglion cells into one of several subgroups based upon some or all of the above criteria. In the first part of this study we propose to examine the morphology of rat retinal ganglion cells diffusely filled with HRP after optic nerve or transscleral injections. Using flat mounted and sectioned retinae, we intend to provide a detailed light microscopic analysis of the various morphological classes of ganglion cells in adult rats and to ascertain, in the early postnatal rat, the period during which adult configurations are acquired. Electron microscopy will be used to correlate the appearance of adult-like morphology with the acquisition of synaptic contacts onto developing ganglion cells. Second, 3H-thymidine will be administered to fetal rats during the period of ganglion cell histogenesis. Autoradiography of thymidine-labeled retinae coupled with HRP filling of ganglion cells will make it possible to determine whether there is a sequential generation of various morphological classes of ganglion cells across the retina. Finally, immunocytochemical techniques will be used to determine the central connections of HRP-filled ganglion cells after central injections of wheat germ agglutinin and/or concanavalin A, two lectins which are retrogradely transported in neurons. We are particularly interested in determining: 1) which cells provide input to more than one visual nucleus; 2) to what extent are abnormal uncrossed retinal rejections which form after neonatal eye removal due to bilateral projection of single cells; and 3) what are the subcortical projections of displaced retinal ganglion cells.