This chest x-ray shows opacification of the left lung field with surgical rib changes and clips seen near the left main stem secondary to a left pneumonectomy. Multiple nodular opacities of varying sizes are seen in the right lung field. These changes are characteristic of metastatic disease. With the history of a left-sided thoracotomy and chest radiograph changes consistent with a pneumonectomy, the rightsided lesions are most likely metastatic lung cancer. There is no clinical evidence of a mucus plug with atelectasis, although the roentgenographic picture of a homogeneous density without air bronchogram with an ipsilateral mediastinal shift is typical of lung atelectasis. The history does not suppo other choices.