The visual capacities of six cats were studied after bilateral stereotaxic lesions which destroyed more than 99 per cent of their optic tracts. Three animals with total lesions were blind. Three others with no more than 1 per cent intact appeared blind in gross behavioral tests but were able to perform a flux discrimination when tested approximately 35 days after the lesion. Despite extensive training they were, however, unable to relearn a pattern discrimination, indicating that the optic tract remaining was insufficient to support pattern vision. © 1967.