Pupillary dynamics were investigated in 41 patients with hemispheric CVD by means of computerized open-loop videopupillography. The patients were alert and showed either abnormal high- or low-density areas on CT scan. Fourteen cases were examined in the acute stage (within 7 days from onset), 28 cases in the subacute stage (between 8 and 28 days) and 11 cases in the chronic stage (over 29 days). In the acute stage, the parasympathetic nervous functions (maximum velocity and acceleration of pupillary constriction) were hyporeactive and showed no significant differences between the ipsilateral and contralateral side of the lesion. In the subacute stage, these functions were significantly more hyperreactive on the ipsilateral side than on the contralateral side, that is, the parasympathetic functions of the healthy hemisphere became significantly improved in comparison with those in the acute stage. In the chronic stage, no significant differences were observed between the two sides. In contrast, the sympathetic nervous function (maximum velocity of dilatation) showed no differences with respect to either laterality or the time course after onset. The above data suggest that bilateral parasympathetic hypofunctions exist in the acute stage of hemispheric CVD, with an ipsilateral improvement of these functions with the passage of time, and that such autonomic dysfunctions may play some role in the pathophysiology of CVD.