The irritable bowel syndrome is one of the most common clinical problems encountered by the generalist and gastroenterologist. The goal of this review is to critically evaluate, based on available peer-reviewed literature, the current status of our understanding of the pathophysiology of the irritable bowel syndrome. The epidemiology of this disorder, including the characteristics of its presentation, natural history and associated phenomena, have been clarified. Differences between those who seek specialist care ('the consulters') and those in the community are now recognized. While, in both, symptoms may be similar in nature and severity; 'the consulters' are differentiated by how they react to their complaints. In terms of pathophysiology, the focus has moved to visceral sensation and central perception and has led to the identification of visceral hypersensitivity, visceral hyperalgesia and abnormal central perception of visceral events. This is not to dismiss dysmotility; subtle abnormalities in gas transit may be closely associated with the induction of certain symptoms. On the psychological front, attention now focuses on such complex issues as somatosization, abuse and response to major life events. Interactions between enteric flora, mucosal inflammation, immune phenomena and the enteric neuro-muscular apparatus also attract interest; the entity of post-infectious irritable bowel is now clearly recognized and there is experimental evidence to suggest a role for inflammation. While the precise aetiology of irritable bowel syndrome remains uncertain, considerable progress has been made, with recent advances in pathophysiology offering hope for the development of new therapeutic approaches.