Because of their high prevalence in clinical practice, the field of gastrointestinal motility has tended to focus its clinical and research efforts on such functional disorders as nonulcer dyspepsia, the irritable bowel syndrome, and functional constipation. Because these disorders are difficult to define and their diagnosis remains exclusively symptomatic, progress has been difficult in these areas, and advances in clinical gastrointestinal motility generally have been hampered. This review attempts to emphasize the prevalence and importance of "organic" motility disorders, ie, those disorders of gastrointestinal motor dysfunction that are to a greater or lesser extent based on defined pathology and pathophysiology. Although some of these disorders are rare, recent dramatic progress has important lessons for motility in general and should point the way toward a greater understanding of the more common motor disorders.