Some studies have demonstrated that the motor symptomatology in sporadic and familial Parkinson's disease was identical. From a physiopathological point of view, and perhaps in the future from a therapeutic point of view, it seems important to determine whether sporadic and familial Parkinson's disease are also similar with regard to cognitive impairment. The aim of the present study was to assess cognitive functions in patients suffering from sporadic and familial Parkinson's disease. Executive functions and memory were investigated in particular. Two groups of 12 patients with Parkinson's disease (sporadic and familial) and 12 healthy controls performed a set of tasks known to evaluate different aspects of executive function and memory. One-way analysis of variance tested for significant group effects, and when justified, post hoc analysis was performed. Cognitive impairment was different in sporadic and familial forms of Parkinson's disease. Indeed, although executive function was impaired in both groups of patients, deficits in tests of explicit memory recall were only observed in patients with sporadic Parkinson's disease. Although the impairment observed in both groups of patients suggests a disruption of the striatoprefrontal circuits, this disruption seems to be quantitatively more important and more widespread in the sporadic patients than in the familial ones. In both patient groups, the deficits probably result from dopaminergic and nondopaminergic deprivation and a greater participation of nondopaminergic factors in patients with sporadic Parkinson's disease could be suggested. In this group, a xenobiotic could be responsible for an acquired metabolic defect involving more widespread structures of the striatoprefrontal circuits, leading to disruption of nondopaminergic loops. Cholinergic deprivation is considered in particular.