The prevalence of psychopathology in patients presenting with functional bowel disorder to the gastroenterology department was determined using formal psychiatric rating scales. There was no evidence of excessive psychiatric disorder compared to a group of patients with peptic ulcer disease. However, greater trait scores for neuroticism and introversion were found in the functional disorder group, together with a greater reporting of life events perceived as negative. Central serotoninergic receptor role in the pathophysiology of functional dyspepsia was assessed using a neuroendocrine challenge test. Buspirone, an azaspirone, stimulates central serotoninergic-1(A) receptors and, as a consequence, releases prolactin, and the extent of prolactin release after the challenge is an indicator of central serotoninergic receptor sensitivity. The mean prolactin response was significantly greater in patients with functional dyspepsia than in healthy controls and peptic ulcer disease patients. The sensitivity of the central serotoninergic receptors was also highly correlated with the degree of delayed solid phase gastric emptying assessed scintigraphically. Finally, dyspeptic symptoms can be reproduced in patients by an intravenous cholecystokinin infusion and severity of response was analysed using a visual analogue scale.