Gastroscopy is the most common test for esophageal, gastric, and duodenal diseases. In what cases is gastroscopy necessary: the first one, when there are gastrointestinal symptoms, such as inflammatory tumors of the stomach, esophagus or duodenal ulcer are considered. Secondly, if there is gastrointestinal bleeding and the cause and site of bleeding are unclear, gastroscopy is needed in this case. Thirdly, if upper gastrointestinal tract lesions are found on imaging, further definitive diagnosis should be made. Fourthly, for people with high risk of upper gastrointestinal tumor or pre-cancerous lesions or pre-cancerous diseases, screening is required. Nowadays, it is advocated that those who are older than 40 years old are generally recommended to undergo gastroscopy as part of their routine physical examination. If there is a family history of upper gastrointestinal tract tumors in high-risk groups, this age can be further advanced. For colonoscopy, colonoscopy is mainly used to observe all the lesions of colorectal diseases from the anus to the ileocecal valve. There are mainly the following conditions that require long-term examination. First, for example, if there is a lump felt in the abdomen, especially if there is a mass in the lower left or lower right abdomen. Second, for chronic diarrhea, or in the case of a change in the shape of the stool. Third, for unexplained cases of wasting and weakness, it is also necessary to conduct a colonoscopy screening. Fourth, for gastrointestinal bleeding, if upper gastrointestinal lesions have been ruled out, it is necessary to conduct a long-term examination. Fifth, unexplained anemia, metastatic tumors in supraclavicular lymph nodes, search for the primary lesion, and blood sampling to find elevated serum CA are all cases that require colonoscopy. Sixth, for people with a family history of colorectal cancer or adenoma or polyps, high-risk groups need to routinely undergo colonoscopy, especially if they are older than 50 years old.