Dysphagia is common in both Parkinson's disease (PD) and progressive supranuclear palsy (PSP). Although it is believed to be more common in PSP, there are no controlled data and no comparison of swallowing function between these two disorders. Our aim was to assess dysphagia and swallow function in patients with PSP and PD. Seven patients with PSP were matched to seven patients with PD on the basis of disease duration. Self-rated dysphagia, movement disorder disability, modified barium swallow results, and abnormalities noted on manometry of the lower esophageal sphincter, esophageal body, upper esophageal sphincter, and pharynx were compared between the two groups. Neither severity nor duration of dysphagia differed between the two groups. Patients with PSP had a significantly greater degree of disability [median (range) Hoehn & Yahr score, 4 (3-5) vs. 2 (1-2); P < 0.002]. Manometric abnormalities were similar for the two groups. Oral-phase abnormalities on modified barium swallow were significantly more frequent in PSP (four patients with PSP vs. no patients with PD; p < 0.005). Pharyngeal abnormalities did not differ. Modified barium-swallow scores correlated well with self-reported dysphagia severity for patients with PSP (r = 0.93; p < 0.05) but not for those with PD (r = 0.42; p = NS). The frequency of abnormalities noted during the oral phase was significantly increased in PSP. It is hypothesized that the sensory information conveyed due to this may account for the better correlation between symptoms and swallowing abnormalities and the belief that swallowing problems are more common in PSP.