Neurophysiology of single neurons in retina, geniculate, and visual cortex of anesthetized Rhesus monkeys have been carried out to understand the neural circuity of color vision. Our results indicate that color contrast detectors in visual cortex are distinctly different than luminance contrast detectors, both of which may be sensitive to the orientation of edges. Both types of detectors can be found in many anatomically distinct sub-areas of prestriate cortex. Both our cortical and subcortical studies suggest a unique way in which these two detectors are formed in visual cortex from color opponent geniculate cells. This new model of primate color vision is defined by specific synaptic circuitry, making it amenable to precise examination. Intracellular studies, primarily in the retina, are being directed to testing this model. We are also developing methods of maintaining and growing human retinal cells in vitro in order to perform neurophysiology on the primate species of greatest concern to us as well as to understanding human retinal disease. This latter approach could lead to a minimization of the use of precious infra-human primates for medical research.