The beta type of ganglion cell can be subdivided in Golgi-stained whole mounts of the cat retina according to the branching level of the dendritic tree in the inner plexiform layer. The dendritic branching level of on-beta cells is nearer to the cell body; that of off-beta cells is about 10 micrometers further outwards. After horseradish peroxidase (HRP) injection into the lateral geniculate nucleus all beta cells were labelled. In this way it is shown that about 55% of all ganglion cells, irrespective of retinal topography, are beta cells. The spatial distribution of on- and off-beta cells was studied from the HRP-labelled material. On-beta cells form a lattice with regular inter-cell spacings; off-beta cells are also regularly arrayed. The two lattices are superimposed independently of each other. Beta cells are commonly assumed to be associated with the resolution of fine detail in the cat vision system. The mosaic of beta cells imposes some constraints and permits some predictions to be made with respect to the cat's visual discrimination.