Chest wall involvement is a rare manifestation of tuberculosis. We present a case of a 66 year old male, farmer, who was admitted to our hospital due to the appearance of a 5 cm in diameter soft tissue mass on his left lower chest wall. After one month, when the patient was admitted again for surgical resection, a three-fold increase of the diameter of the mass was observed. A percutaneous biopsy and drainage were performed and the pus was microscopically examined. The results revealed the presence of mycobacterium tuberculosis (Ziehl-Nielsen stain). The patient was started on chemotherapy for tuberculosis. This unusual manifestation of tuberculosis should be a part of the differential diagnosis in patients presenting with a chest wall mass. CT and MRI examinations are the best imaging procedures to provide useful information about the extent and the nature of the disease. Pneumon 2006; 19(4):376-380.