Evidence is presented of gradients between nasal and temporal areas of the cat's retina in the properties of their ganglion cell populations. Mean ganglion cell size is greater in temporal retina than in nasal retina, partly because the alpha- and beta-cells of temporal retina are distinctly bigger than their counterparts in nasal retina, and partly because more medium-sized cells, and fewer small cells, are to be found in temporal retina. This high proportion of medium-sized ganglion cells may reflect a high proportion of beta-cells or of the medium sized gamma-cells described by Stone and Clarke ('80). Several of these differences can be related to prior morphological, electrophysiological, and behavioural observations in the cat, and similar differences have been reported in several other mammalian species. Evidence is presented that, in the cat, at least some of these differences are less marked near the vertical meridian of the retina than more temporally or nasally. The present results may therefore, be evidence of a nasal-temporal gradient in retinal structure and funtion common to many mammals, and distinct from previously recognised gradients in ganglion cell properties related to the area centralis and visual streak specialisations.