Abnormal postprandial cardiovascular responses such as postprandial hypotension (PPH) occur in primary autonomic failure and contribute significantly to morbidity. The extent and frequency of PPH and its relationship to the parkinsonian state in idiopathic Parkinson's disease (IPD) is unknown. By studying 20 patients with IPD (without autonomic failure) and 16 age-matched controls after both groups ingested a standard isocaloric balanced liquid meal we have shown that supine PPH complicates IPD and is reduced to marked worsening of the parkinsonian state as measured by a cumulative score of tremor, rigidity, bradykinesia, posture, and gait, Furthermore, significant postural hypotension is unmasked that results in posturnal intolerance due to presyncopal symptoms. Our study in posturnal intolerance due to presyncopal symptoms. Our study indicates that, in patients with IPD, ingestion of a meal may lead to abnormal postprandial cardiovascular responsea and aggravation of the parkinsonian state. The underlying mechanisms are unclear, although vasodilatory gut peptides released in response to food ingestion may be contributory.