We report the successful surgical treatment of chronic expanding hematoma in the chest. Four patients who had previously undergone artificial pneumothorax, thoracoplasty or tumor extirpation more than 30 years earlier recently became aware of a slowly growing mass. Chronic expanding hematoma which developed into very large masses over a long period of time were thus successfully resected. These patients are now all in good health with no recurrence after the operation. It is important to monitor such patients' laboratory data for hemostasis including the platelet cell counts, the % prothrombin time and the D-dimer, both before and immediately after operation, and the intraoperative bleeding volume.