The effects of domperidone, a peripherally acting dopamine antagonist, were compared with those of placebo in a double-blind randomized study in 16 patients with idiopathic gastric stasis, chronic symptoms of "nonulcer dyspepsia" (including nausea, vomiting, and abdominal pain), and altered gastroduodenal motility. Patients received either domperidone or placebo orally (20 mg before meals and at bedtime) for six weeks. Symptoms were assessed by daily diaries kept by the patients for two weeks while receiving no medication for their gastrointestinal complaints (baseline), and throughout the six-week treatment phase. Studies of gastric emptying of a radiolabeled solid-phase meal were performed at baseline and six weeks after treatment. All patients had delayed gastric emptying at baseline, defined as a half-emptying time of more than mean + 1 SD (from studies of normal controls). An 18- to 24-hr recording of gastroduodenal motor function during fasting was also performed at baseline and after six weeks of either domperidone or placebo treatment. After six weeks of treatment, the symptom scores significantly improved in the domperidone group (P less than 0.05), but not in the placebo group. Gastroduodenal motor activity was unchanged from baseline recordings after six weeks. Solid-phase gastric emptying also showed no improvement in either the domperidone or placebo group of patients. Although domperidone therapy had no significant effect on motility, it appears to be an effective drug for the treatment of the symptoms of nonulcer dyspepsia.