We aimed to evaluate oral hygiene in patients with Parkinson's disease (PD). The incidence of periodontal disease and numbers of caries and remaining teeth were checked in 89 consecutive 60 to 79-year-old patients with PD and compared with two other patient groups: 68 patients with mild neurological disease, and 60 with acute ischemic stroke. Patients with PD had fewer remaining teeth, more caries and a higher incidence of deep periodontal pockets. The frequency of patients with PD with untreated caries was high at Hoehn and Yahr stage II and above, and frequency tended to increase in patients who had low compared to high mini-mental state examination scores. Careful attention should be paid to the oral hygiene of patients with PD, even in the early stages of the disease.