The effects of chronic, atropine-induced cycloplegia on the binocularity of neurons in the striate cortex of adult cats was studied using standard microelectrode recording techniques. Untreated control subjects, binocularly treated subjects, and subjects treated monocularly for less than 35 days exhibited normal ocular dominance distributions. Subjects treated monocularly for 39 days or longer demonstrated a substantial decrease in the proportion of binocularly innervated simple cells. The loss of binocularity did not require visual experience; since monocularly treated subjects kept in light-proof cages for the duration of the treatment period, showed sin equivalent decrease in cortical binocularity. It was concluded that the loss of binocularity was caused by an asymmetrical paralysis of accommodation.