Achalasia is the best understood of the motor disorders described in this chapter. The pathogenesis involves loss of intramural neurones, a process that subsequently results in poor lower sphincter relaxation and atony of the oesophageal body. Treatment is appropriately focused on mechanical or pharmacological alleviation of LOS obstruction. In contrast, the pathophysiology of DOS and the non-specific disorders remains poorly understood. Some of the non-specific disorders, such as the vigorous contraction wave abnormalities (including 'nutcracker oesophagus'), appear closely related to DOS. Treatment for patients with these findings has been based on assumptions about mechanisms of symptom production. The non-specific disorders are common in referred patients with oesophageal symptoms, and the importance of these findings deserves further study. We use a method for categorization of these manometric abnormalities which aids understanding of this difficult area and recommend its more widespread use.