1. Three distinct morphological types of cat retinal ganglion cells have been identified and categorized as alpha, beta and gamma. Alpha ganglion cells have dendritic field diameters from 180 to 1000 mum; beta, about 25 to 300 mum; gamma, 180 to 800 mum, possibly more.2. The dimensions of the alpha and beta ganglion cell dendritic fields increase monotonically from the central area outwards to the periphery; those of the gamma cells do not. Seemingly a spectrum of sizes of the gamma cells is found at most locations in the retina.3. All three morphological types of ganglion cells are found in the central area.4. Possible further anatomical types of ganglion cells are discussed. Correlations are suggested between the morphological category alpha cells and the physiological class Y cells; between beta cells and the X cells and between the gamma cells and the W cells.