Background/Aims : The role of autonomic dysfunction in patients with functional dyspepsia has not been completely understood. The purposes of our study are (1) to prospectively assess the abnormalities of the autonomic function in patients with functional dyspepsia and (2) to assess whether the presence of autonomic dysfunction in patients with functional dyspepsia correlates with the presence of visceral hypersensitivity or with the severity of dyspeptic symptoms. Methods : Twenty eight patients with functional dyspepsia (4 men and 24 women; age range, 29-57) and 14 healthy volunteers without gastrointestinal symptoms (6 men and 8 women; age range, 23-61) were included in this study. All patients and controls were submitted to a battery of five standard cardiovascular autonomic reflex tests and gastric barostat tests. A modified version of the Glasgow Dyspeptic questionnaire was used in this study. Results : (1) Autonomic function tests showed that both sympathetic and parasympathetic scores of dyspeptic patients were significantly higher than those of the control group. (2) Visceral hypersensitivity could be confirmed in some of our dyspeptic patients in response to proximal gastric distension, demonstrating lower pain threshold in this group. (3) We could not find significant association between the presence of autonomic dysfunction and the presence of visceral hypersensitivity or severity of dyspeptic symptoms in patients with functional dyspepsia. Conclusion: Autonomic dysfunction was more prevalent in dyspeptic patients than in the control group. However, it did not correlate with the presence of visceral hypersensitivity or severity of dyspeptic symptoms. It is suggested that a defect in the spinal region or at the CNS level may be a major mechanism of visceral hypersensitivity in functional dyspepsia.