Hypersialorrhea is frequently reported in patients with idiopathic Parkinson's Disease (PD). Excessive production of saliva, swallowing difficulties, or both could explain this complaint. Dopamine (DA) has been shown to modulate salivary secretion in a number of vertebrate and invertebrate species. The present study was performed to compare the unstimulated salivary flow in 83 patients with PD (8 untreated and 75 treated with levodopa + DA agonist) and in 65 age- and sex-matched control subjects. The Mann-Whitney U-test showed a significantly lower salivary flow in treated patients with PD (535 +/- 42 mg/2 min) (p < 0.002) and de novo patients (447 +/- 141) (p < 0.03) compared to controls (834 +/- 68 mg/2 min) with no relation with age or sex. Finally, the present study of reduced salivary flow in PD suggests that complaints of hypersialorrhea are not caused by a salivary defect, but could be explained by difficulties in swallowing. The decrease in salivary flow could be explained by autonomic dysfunction in PD.