We have investigated the mapping of the two major classes of retinal ganglion cells, color-opponent and broad-band, onto striate cortex (VI) of macaque. There is a one to one relationship between color-opponent retinal ganglion cells and parvocellular cells of the Lateral Geniculate Nucleus (LGN), which we call the P-cell system. A similar relationship holds for broad-band ganglion cells and magnocellular cells of the LGN, which we call the M-cell2 system. There is a nearly constant number of P-cells projecting to each mm of VI, whereas that for M-cells increases with eccentricity. In VI the cytochrome-oxidase puffs have been thought to define a module of function. Our results indicate that these units are better described as a P-cell module. The VI-point-image refers to the maximal area activated by a point in visual space. A constant number of M-cells project to the point-image area, independent of eccentricity. In single-cell recordings from ganglion cells of macaque retina we have examined the effects of the onset and offset of moderately intense, large field backgrounds. Broad-band (color non-opponent) cells show strong transient desinsitizations to both onset and offset of the background lights. In contrast, the behavior of color-opponent ganglion cells varied with the cell subtype. Blue-center cells showed large desensitizations at the onset and offset (transient tritanopia) of the background, while green-center cells showed very weak desensitization. Red-center and yellow-center cells showed an intermediate behavior