BACKGROUND: Gastro-oesophageal reflux disease (GORD) is extremely common, with at least 1 in 10 people in the general population reporting heartburn and acid regurgitation on a weekly basis. GORD can also be associated with a variety of atypical symptoms, including chest pain, chronic cough, and laryngopharyngeal symptoms. The causes of GORD are multifactorial, and the severity of symptoms is influenced by peripheral and central factors, including psychosocial stress and anxiety. Therefore, for a variety of reasons, no single investigation provides a definitive diagnosis, and standard treatment with acid suppressants is not always effective. SUMMARY: This review introduces the Lyon Consensus, now in its second iteration, a classification system that provides a "conclusive" positive or negative diagnosis of GORD by integrating the results of endoscopy, ambulatory reflux monitoring, and high-resolution manometry. Different algorithms are applied to patients with high and low pre-test probability of a causal relationship between reflux episodes and patient symptoms. The results of these studies identify patients with "actionable" results that require escalation, revision, or discontinuation of GORD treatment. Guidance is provided on the range of conservative treatments available for GORD, including dietary and lifestyle advice, antacids and alginates, and drugs that suppress acid secretion. KEY MESSAGES: GORD is a common disorder; however, the causes of reflux and symptoms can be complex. As a result, the diagnosis can be missed, and management is sometimes challenging, especially for patients with atypical symptoms. The Lyon classification establishes a conclusive diagnosis of GORD, based on results of endoscopic and physiological investigation. Typical symptoms usually respond to empiric use of alginate-antacid preparations and acid suppression; however, the management of treatment refractory symptoms is tailored to the individual.