Performance on tasks evaluating "executive and attentional" processes presumably subserved by prefrontal cortex were compared in patients with progressive supranuclear palsy and with age- and education-matched control subjects. The results indicated that patients with progressive supranuclear palsy were particularly impaired when a task required sequential movements, conceptual shifting, monitoring the frequency with which stimuli are presented, or rapid retrieval of verbal knowledge. These deficits could not simply be accounted for by slowed information processing or by a deficit in representational knowledge. Conceivably, "weak activation" of frontal lobe representational knowledge characterized by an observed attentional deficit results in the neuropsychological impairments noted in patients with progressive supranuclear palsy. The oral administration of physostigmine, under double-blind placebo-controlled conditions, did not facilitate executive or attentional performance as evaluated by our tasks.