The modified Eloesser procedure or open-window thoracostomy is a surgical treatment for chronic pleural empyema in which a relatively permanent drainage opening is created in the chest wall. The chest radiographs and CT scans of 13 patients who underwent a modified Eloesser window procedure were studied. On chest films, the Eloesser window characteristically appeared en face as an elliptical or crescent-shaped radiolucency with sharp superior and ill-defined inferior margins. It appeared in profile as a downward-sloping chest-wall defect with round superior and straight inferior margins. The first radiographs made after surgery often showed potentially confusing densities caused by the iodinated gauze used to pack the drained empyema cavity. On sequential chest films, the defect in the chest wall was always detectable, while the pleural cavity diminished in size and usually disappeared within 6 months. This analysis shows that the postoperative chest radiographs and CT scans in patients having the Eloesser window thoracostomy have features that are characteristic of the procedure.