The irritable bowel syndrome (IBS) is characterized by alimentary and non-alimentary symptoms; the aim of this study was to assess the clinical value and discriminant function of non-alimentary symptoms in the irritable bowel syndrome. Alimentary and non-alimentary symptoms, estimated daily dietary fibre intakes, ability to express personal feelings, anxiety and depression ratings, and life events and difficulties inventories were compared in 128 hospital out-patients with IBS and 113 age and sex matched control subjects not seeking health care, randomly recruited from the community. Alimentary symptoms correlated closely with those non-alimentary symptoms often associated with the hyperventilation syndromes, difficulties in expressing personal feelings and anxiety, and depression ratings. Life events and difficulties, and estimated daily dietary fibre intakes did not differ significantly between patients and controls. With the exception of abdominal bloating, no significant gender differences were observed in IBS symptoms in either the IBS or control groups. The irritable bowel syndrome is one facet of a more general condition of illness behaviour which includes the hyperventilation syndrome and an inassertiveness in expressing personal feelings. Though non-alimentary symptoms did not improve diagnostic accuracy beyond that achieved by a combination of alimentary symptoms, their recognition provides alternative approaches to the management of refractory IBS.