[1] Functional dyspepsia: a clinical state with clinical symptoms of ulcer disease, but without the presence of peptic ulcer in the upper gastrointestinal tract by all instrumental examinations. Patients complain of belching, belching acid, eructation, nausea, vomiting or gas, and discomfort, heartburn or pain in the upper and middle abdomen are mostly present. However, the site of pain is mostly variable and can be triggered or aggravated by psychological factors. Symptoms may improve with medical anti-ulcer medication, but complete symptom relief is rarely achieved. [2] Reflux esophagitis: There may be burning pain in the precordial region or epigastrium, acid reflux, belching, rather like a peptic ulcer, but it may be accompanied by painful swallowing. If complicated by a septal hernia, the pain often appears in the supine position after eating and disappears in the standing position. [3] Chronic gastritis: there may be abdominal pain, abdominal distension, heartburn, acid reflux and other symptoms. It is difficult to differentiate from peptic ulcer, mainly based on gastroscopy or barium meal angiography. [4] Gastric cancer and gastric ulcer malignancy: the course of gastric cancer is short, the disease progresses rapidly, and patients are often accompanied by wasting, anemia, black stool, etc. However, it is difficult to clarify from clinical symptoms, and must rely on barium meal angiography and gastroscopy, especially mucosal biopsy for pathological examination under gastroscopy. [5] Gastrinoma: For recalcitrant, fulminant gastroduodenal ulcers that are not controlled by conventional medical therapy, the possibility of gastrinoma must be considered. Pancytopenia (not only involving the gastroduodenum) and multiple (more than one ulcer in one organ) ulcer formation is another characteristic of gastrinoma. Highly abnormal elevated serum gastrin levels suggest the diagnosis of gastrinoma. [6] Chronic biliary disease: Chronic biliary disease can cause dyspeptic symptoms or right upper abdominal pain, which is sometimes misdiagnosed clinically as peptic ulcer. b-mode ultrasound with X-ray cholangiography can clarify the diagnosis. [7] Chronic pancreatic disease: Although chronic pancreatic disease can have dyspeptic symptoms, it is generally not misdiagnosed. However, sometimes chronic pancreatitis can also be accompanied by peptic ulcer. The more difficult differentiator is chronic pancreatitis due to penetration of chronic penetrating ulcers into the pancreas, but the patient does not have a history of acute pancreatitis and has an episode with elevated serum amylase that is far less severe than primary pancreatitis. Pancreatic cancer can cause pain in the mid-upper or left upper abdomen, but the pain often appears or worsens in the supine position and relieves or disappears in the sitting position with the upper body tilted forward. b-mode ultrasound with CT scan often provides a definitive diagnosis. [8] Heart disease: Patients with coronary arteriosclerotic heart disease may present with dyspeptic symptoms such as abdominal distention after eating, but without the rhythmicity of ulcer disease, which is not relieved by alkaline medications and is relieved by crown-dilating drugs. Congestive hepatomegaly due to congestive heart failure may cause right upper abdominal pain due to periportal traction, but it is persistent and dull, and the pain disappears after the heart failure is relieved. ECG, echocardiography and other tests can help to clarify the diagnosis.