Gastroesophageal reflux disease (GERD) is a chronic disease affecting up to 40% of people in the Western world. Risk factors associated with GERD include age and lifestyle habits, although the clinically relevant contribution of many of these factors is unclear. In GERD, refluxed gastric acid damages the oesophageal mucosa, generally when the pH falls below 4. GERD patients present a variety of symptoms, most commonly heartburn and regurgitation. Oesophageal complications associated with GERD include erosions, ulcers, peptic strictures, and Barrett's oesophagus which is implicated in the development of oesophageal adenocarcinoma. Diagnosis of GERD is problematic due to the range of symptoms which may be presented to the physician and symptom severity is frequently unrelated to disease severity. While endoscopic monitoring may be used to assess the presence and severity of GERD, a lack of visible damage does not necessarily indicate an absence of GERD. Techniques used to diagnose GERD include addition of an acid solution into the oesophagus in order to replicate symptoms (Bernstein test) or 24-hour intra-oesophageal pH monitoring. Proton pump inhibitors are effective in the treatment of GERD, acting to reduce the acidity of the gastric juice and hence reduce oesophageal damage and symptoms associated with GERD. Symptoms most indicative of GERD are those associated with erosive oesophagitis, including heartburn and acid regurgitation. Less common GERD-associated symptoms include chest pain, a range of ear, nose and throat conditions, and asthma. In contrast to perceptions of the disease as 'merely' heartburn, the impact on patients' quality of life can be profound. Increasing awareness of GERD by health care professionals has led to improved diagnosis and a greater appreciation of the need for maintenance therapy.