How long a 65-year-old man can survive with fluid in his lungs is related to the cause of the patient’s illness, physical fitness, and treatment methods, and cannot be generalized. Pulmonary effusion in 65 year olds is pleural effusion and can be caused by a variety of factors, including pneumonia, tuberculous pleurisy, congestive heart failure, hypoproteinemia, and medications. If it is benign and due to medications, it is usually curable and does not affect the patient’s life expectancy. If it is caused by tuberculous pleurisy, anti-tuberculosis treatment is required for 6-12 months after diagnosis, and some patients can usually be cured with 18 months of treatment. If the malignant pleural effusion is caused by pleural metastasis of lung cancer or pleural metastasis of malignant tumors in other parts of the body, the patient is usually in the advanced stage of cancer, and the survival time of this kind of patients is shorter, which can be from a few months to a year, and usually not more than 2 years. Therefore, it is recommended that patients actively undergo various examinations to find out the cause of pulmonary effusion, and if it is caused by the primary disease, the primary disease should be actively treated.