Despite the high prevalence of Parkinson's disease, the pathophysiology of its gastrointestinal symptoms remains poorly understood. OBJECTIVES: to evaluate swallowing and defecatory function in patients with Parkinson's disease and age- and sex-matched controls and to correlate objective findings with subjective symptoms. METHODS: The following studies were performed on 13 patients with Parkinson's disease and seven controls: extrapyramidal function assessment, gastrointestinal symptom survey, videoesophagram, colon transit study, defecography, and anorectal manometry. RESULTS: Abnormal salivation (frequency, %, control vs. Parkinson's disease: 14 vs. 77, p < 0.05), dysphagia (14 vs. 77, p < 0.05), constipation (14 vs. 31, p < 0.05), and defecatory dysfunction (29 vs. 77, p < 0.05) were more common among Parkinsonian patients. However, videoesophagographic abnormalities were equally common in both groups. Colon transit time was significantly prolonged in the Parkinson's disease group. Altered puborectalis function was noted on defecography in 31% of Parkinson's disease subjects, but in none of the controls (p < 0.05). Anorectal manometry identified several abnormalities in the Parkinson's disease group, which included decreased basal anal sphincter pressures, prominent phasic fluctuations on squeeze, and a hyper-contractile external sphincter response to the rectosphincteric reflex. Many patients exhibited both slow transit and manometric abnormalities, and symptoms were poor predictors of test results. CONCLUSION: In this group of patients with mild to moderate Parkinson's disease, videoesophagographic abnormalities were not confined to the patients with Parkinson's disease. Studies of colonic and anorectal function, in contrast, identified a number of abnormalities. Therefore, colonic and anorectal dysfunction appears to be an early gastrointestinal manifestation of Parkinson's disease, and may represent the direct involvement of the gut by this disease process.