Visual-spatial deficits are often associated with Parkinson's Disease (PD). Recent theories suggest that frontal-basal ganglionic dysfunction affects cognition in PD. Although this hypothesis does not entirely explain spatial deficits in PD, the inappropriate utilization of cues associated with executive dysfunction may induce spatial deficits. Alternatively, the vestibular system is also involved in spatial cognition, and vestibular dysfunction may affect visual-spatial ability in PD. To test these hypotheses, we administered the Water Jar Test, while perturbing vestibulo- proprioceptive input. Non-demented PD patients were significantly less accurate than controls in judging horizontal, and appeared to inappropriately utilize cues. No group effect was found for head tilt. These findings suggest the visual-spatial difficulties seen in PD are related to executive dysfunction that is associated with a disruption of the frontal-basal ganglionic and frontal-parietal systems. (C) 2000 Elsevier Science Ltd.