Cognition and performance of patients with localized and diffuse brain damage was evaluated through the application of objective perceptual testing. A series of visual perceptual and verbal tests, memory tests, as well as reaction time tasks were administered to the patients by logic programming equipment. In order to avoid a bias due to communicative disorders, all responses were motor, and achievement was scored in terms of correct identification and latencies of response. Previously established norms based on a large sample of non-brain-damaged hospitalized patients served to standardize the performance of the brain-damaged patient since preliminary results showed that age and educational level constitute an important variable affecting performance of the control group. The achievement of brain-damaged patients, corrected for these factors, was impaired significantly in all tests with respect to both recognition and speed of performance. Lateralized effects of brain damage were not significantly demonstrated. However, when the performance was analyzed with respect to the locus of visual input, it was found that patients with right hemispheric lesions showed impairment mainly on perception of figurative material, and that this deficit was more apparent in the left visual field. Conversely, patients with left hemispheric lesions tended to show impairment on perception of visually presented verbal material when the input was delivered to the right visual field.