Recordings were made from single retinal ganglion cell somas in cats whose visual cortical areas 17 and 18 were damaged on the day of birth or in adulthood. Neonatal lesions produced a 78 percent loss of X-cells in the retina, while lesions made in adulthood produced a 22 percent loss. Y-cells and W-cells were unaffected. This retinal abnormality needs to be considered when interpreting studies of behavioral deficits and neural mechanisms of recovery after damage to the visual cortex.