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Topographical patterns of event-related potentials were compared on a visual display terminal for a data-input task and a number-comparison task. Maximum negative peaks were found in the frontal and central regions for the former but at midline locations for the latter. Latencies were shorter in the occipital regions than in the frontal regions for the former and the opposite pattern was found for the latter. An analysis of variance indicated that hemispheric location significantly affected the amplitude of peaks. On the other hand, latencies were affected by the task, frontal and occipital regions, and their interaction. These results suggest that a pattern of the topographic display of event-related potentials can be used as an objective means for classifying visual tasks.