Abstract Systemic administration of anticholinergic agents impairs cognitive performance in animals and man. The anticholinergic, scopolamine, has profound effects on peripheral and central cholinergic function, making interpretation of its effects on cognitive performance difficult. To circumvent this problem, scopolamine was administered directly to the central nervous system of rhesus monkeys using a subcutaneously implanted infusion pump connected to a cannulae directed toward the right lateral ventricle. Intracerebroventricular (ICV) infusion of scopolamine (0.004, 0.012, 12.5, and 40.0 μg/kg/h) produced a dose-dependent decrease in the number of responses on a continuous performance task. Response decrements produced by scopolamine were seen mainly during the last half of the test session and at short stimulus durations. These data suggest that scopolamine produces a deficit in sustained attention or slowing of information processing that is mediated through direct central cholinergic blockade in the rhesus monkey.