Conventional oesophageal manometric studies are open to criticism in that they take place on fasted immobile subjects in the artificial setting of a motility laboratory. A new 24-h pH and motility recording system combined with computerized data analysis was used to study patients with gastro-oesophageal reflux disease and oesophageal motor abnormalities under ambulant conditions. Acid reflux episodes were found to be precipitated by a variety of events with recognizable pressure patterns. Acid clearance abnormalities were demonstrated in patients with erosive oesophagitis but were confined to those with abnormal oesophageal motor function. Improved diagnostic accuracy was demonstrated in the recognition of oesophageal motor disorders.