Since sialorrhea was initially described, it has been associated with Parkinson's disease (PD) but until now little is known about its pathophysiology. The authors studied parotid gland activity using scintigraphic analysis on 14 PD patients with sialorrhea and in eight healthy persons with matching ages. There was no difference between uptake and intra-glandular distribution by the parotid gland in the two groups but the parotid excretion speed in the PD patients was greater than that observed in healthy individuals. Our results reject the hypothesis of PD productive sialorrhea and point to retention sialorrhea due to the increase of saliva excretion velocity.