Deficits in visual discrimination were examined in 30 combat soldiers with head wounds, 20 of whom had unilateral lesions (10 right and 10 left) of the posterior cerebral hemispheres and 10 of whom had frontal lobe wounds, left, right or bilateral. Seven of the patients with posterior lesions, but none with frontal lesions, showed visual spatial disorientation as demonstrated by a shift in the peak of the stimulus generalization gradient of an experimentally conditioned sensory discrimination. The peak shift occurred to the side opposite the cerebral lesion in all cases, and the deficit did not occur when the task was presented as a match to sample.