Old tuberculosis is usually not infectious and is a scarred lesion that remains after a previous tuberculosis infection has been cured and the lesion has been absorbed. Obsolete TB is usually found on chest x-ray or CT, and the TB lesions are relatively stable. However, because they may contain dormant Mycobacterium tuberculosis. When the body’s immunity decreases or other diseases develop, the balance between the body’s immunity and the virulence of Mycobacterium tuberculosis may be disrupted, causing the patient to develop the disease again. In this case, the patient’s existing lesions may increase or even develop new lesions, such as cavities, exudates, and proliferative lesions, before they become infectious. Patients with old tuberculosis should be reviewed regularly for any recurrence so that it can be detected early. Usually, they should strengthen their immunity by enhancing nutrition, taking rest, and exercising properly.