In the clinic many patients will say that they have chest pain, especially many people happen to have pain under the left side of the chest. In fact, from the anatomical structure of the left lower chest, there are many possible causes of pain, as follows: 1, common costochondritis, and intercostal neuralgia, which may be related to trauma, cold, exhaustion, and excessive activity; 2, aseptic inflammation, such as fasciitis of the muscles may also cause pain below; 3, the thoracic spine, such as compression fractures, may also flee to the left side of the lower chest, just like a belt-like pain 4, consider heart problems, because the heart is on the left, if there are heart diseases, such as angina or heart attack, may also cause left chest pain; 5, respiratory problems, pleurisy or lung diseases, will also cause pain under the left chest; 6, the left side of the pancreas or the abdominal cavity of the stomach, intestines, liver, bile, sometimes problems will also run to the left side of the chest pain. Therefore, if a patient has left-sided chest pain in the outpatient clinic, it must be combined with medical history, clinical physical examination, and some necessary auxiliary imaging tests to determine what is going on.