Men with vague pain in the left chest have to make a specific judgment based on the nature of the pain, frequency of attacks, duration and accompanying symptoms. The left chest may involve tissues and organs such as the heart, lungs, breast, rib cartilage, etc. The cause of hidden pain in the left chest requires identification of these organs. 1, heart: more common is coronary heart disease. Episodic chest pain is a characteristic of coronary artery disease. The typical pain site is behind the sternum. However, the pain may also radiate to the left chest. The nature of the pain is typically crush-like, mostly accompanied by significant chest tightness, and some patients have a sense of near death, often forcing patients to stop activities immediately. There are many triggers for the onset of symptoms, such as going upstairs, rapid walking, exertion, full meal, cold, emotional excitement, etc. The symptoms may be relieved by quiet rest. Other things such as myocarditis and pericarditis can also cause pain in the left chest. 2, lung: more common lung infection, spontaneous pneumothorax, pleurisy, lung cancer, etc. Spontaneous pneumothorax often has tearing-like pain when it first occurs. Lung cancer is persistent and severe pain. Pain due to lung causes is mostly aggravated by breathing or coughing. 3.Breast: Male breast cancer may cause pain in the left chest. Painless lumps can be felt in the early stage of breast cancer, and local orange peel-like skin changes can be seen in the later stage. 4.Other: costochondritis may cause chest pain with local pressure pain but no redness or swelling; herpes zoster pain distributed along one side of intercostal nerve with severe pain, and the pain does not exceed the midline of body surface. Cardiac neurosis needs to be considered in those who fail to find organic pathology even after functional examination. There are many causes of left chest pain in men that require attention to timely medical care to rule out the possibility of fatal disease.