Responses of single cells in the striate cortex of a behaving monkey were studied while the eye movements of fixation were monitored with high precision. Receptive fields of cortical neurons moved in space with the eye. When the eye position signal was used to stabilize the image on the retina, response rates were more vigorous and more reliable. When the image was not stabilized, the estimates of receptive field activating areas were influenced (usually inflated) in unpredictable ways. With stabilization, small receptive fields can be studied and powerful surround interactions become apparent.