To test the hypothesis that post-polio fatigue and its concomitant cognitive deficits are associated with an impairment of attention and not of higher-level cognitive processes, six carefully screened polio survivors were administered a battery of neuropsychological tests. Only subjects reporting severe fatigue, and not those with mild fatigue, demonstrated clinically significant deficits on all tests of attention, concentration, and information processing speed while showing no impairments of cognitive ability or verbal memory. These findings suggest that an impaired ability to maintain attention and rapidly process complex information appears to be a characteristic in polio survivors reporting severe fatigue, because these deficits were documented even when their subjective rating of fatigue was low. This finding supports the hypothesis that a polio-related impairment of selective attention underlies polio survivors' subjective experience of fatigue and cognitive problems.