Gastric adenocarcinoma continues to be a frequent cause of death in the world and is the 16th most common cancer in the UK. The most common stages in the progression to gastric adenocarcinoma are gastric atrophy (GA) and gastric intestinal metaplasia (GIM), which are collectively known as chronic atrophic gastritis (CAG). These conditions are principally caused by Helicobacter pylori infection and less commonly by autoimmune gastritis. The key to having a significant impact on the prognosis of gastric adenocarcinoma and its economic burden is to accurately identify individuals at greatest risk and intervene with recognised efficacious treatments, including endoscopic resection, before cancer is established. The British Society of Gastroenterology (BSG) endoscopy committee agreed to create a guideline to provide statements and recommendations on the prevalence, risks, diagnosis, treatment, surveillance and screening of gastric premalignant and early gastric malignant lesions. The principal patient group are those found to have GA, GIM, gastric epithelial dysplasia or early gastric adenocarcinoma limited to the mucosal or superficial submucosal layers. The target users include gastroenterologists, GI surgeons, pathologists, endoscopists and general practitioners.