Dysphagia and drooling of saliva are frequent symptoms in Parkinson's disease (PD), occurring in one-half and three-quarters of all patients, respectively. Aspiration related to swallowing is a major cause of morbidity and mortality in PD. Defects in oral, pharyngeal, and esophageal phases of swallowing have been documented in patients with PD, and these defects precede symptoms. This paper reviews the current knowledge concerning swallowing abnormalities in PD. The pathogenesis of dysphagia and drooling of saliva is multifactorial, involving cognitive and psychological changes in addition to abnormalities of the extrapyramidal and autonomic nervous systems. Videofluoroscopic imaging of the upper esophageal sphincter and pharynx during mastication and swallowing has been the basis of our understanding of the mechanical malfunction present in patients with PD. Manometric abnormalities of the esophageal body and lower esophageal sphincter have also been documented. The use of combined manofluoroscopy to examine the upper esophageal sphincter and pharynx in PD offers great promise both in understanding the defects and directing therapy. Voluntary airway protection techniques may reduce aspiration, but they need to be tested in a clinical study. Such maneuvers may reduce the morbidity seen in PD.