Gastrointestinal (GI) motility is very frequently disturbed in Parkinson's disease (PD), manifesting chiefly as dysphagia, impaired gastric emptying and constipation. All these symptoms - constipation in particular - may precede the clinical diagnosis of PD for years. In the future, these symptoms might serve as useful early indicators in the premotor stage. Disturbed gastric emptying is an important factor in unpredictable fluctuations. The most likely causes are degenerations of the dorsal vagal nucleus and the intramural plexus of the whole intestine. These degenerations are likely to develop prior to the degeneration of dopaminergic neurons of the substantia nigra. Diagnosis includes history, clinical examination, barium meal, breath test, scintiscan of stomach, and colonic transit time. Therapeutic efforts are limited when it comes to disturbed motility of the upper GI-tract. Hypersalivation can be reduced by anticholinergics or botulinum toxin injections; motility of the upper gastrointestinal tract is only moderately impacted on by domperidone. In constipation, the conservative therapeutic option is administration of macrogol (polyethylene glycol), which leads to marked improvement.