The "deprived" cortex of monocularly deprived rats showed a considerable diminution in response to specific visual stimuli. Many neurons (57.7%) in the "deprived" cortex did not respond to any visual stimuli, and 29% reacted nonspecifically to any stimulus anywhere in the visual field (indefinite cells). In comparison, 7.4% neurons in the "nondeprived" cortex were not responsive to visual stimuli and 41.3% gave indefinite response. In the "normal" cortex 51.1% of the cells were motion, orientation, or direction selective while the number for the "deprived" cortex was 13.3%. Spontaneous activity of the "deprived" cells was of the same rate and pattern as was that of the "normal" cells. Receptive field properties of cells from the "deprived" cortex that were responsive, were similar to those of cells from the "normal" cortex. They were large and showed pure "on" "off" or "on-off" regions; others were of the complex type with mixed response regions. All responded optimally to moving stimuli.