Abstract Acid gastro-oesophageal reflux occurs when the lower oesophageal sphincter is incompetent, but oesophagitis caused by reflux of duodenal content implies incompetence of both the pyloric and gastro-oesophageal sphincters. The term ‘alkaline’ reflux oesophagitis was coined long before objective analysis was made-of bile in the stomach and oesophagus, and well before pH monitoring was introduced. Surgical procedures to divert bile from the stomach and oesophagus were developed on a clinical basis and gave encouraging results in the management of peptic oesophageal stricture. Alkaline oesophagitis is well recognized after gastric surgery and the entity ‘primary pathological duodenogastric reflux’, although contested by some, attracts growing support. Recent evidence suggests that the complications of Barrett's oesophagus may be related to duodenogastro-oesophageal reflux. Probes designed to measure gastric and oesophageal bile salts have recently been developed and may give more information in the future.