The proposed experiments address the important question of whether receptive field properties in early visual cortex are dynamically altered by the visual scene surrounding the receptive field. There is a growing appreciation that the neural representations generated in V1 and V2 are far more elaborated than those suggested by superficial characterization of the classical receptive field. Our understanding of cortical representations and cortical processing will be far from complete until we understand the range and magnitude of the effects of stimuli outside the classical receptive field. The proposed experiments will examine the effects of visual context on the binocular disparity sensitivity of neurons in VI and V2 of trained, behaving monkeys. Although there is no discussion of why disparity is the parameter of choice for these experiments (given that it is more difficult to present and control than most), a set of interesting and tractable psychophysical disparity phenomena related to visual cortex serve as the basis for the proposed experiments. The particular phenomena and stimuli are well selected, and should provide valuable information about the effects of visual context on sensory responses.