Left hemorrhagic pleural effusion was the presenting sign of painless aortic dissecting aneurysm in two elderly hypertensive patients. Computed tomography (CT) of the chest revealed the aneurysmal dilatation of the thoracic aorta and an intimal flap connecting its descending part with the left pleural space. The patients were treated conservatively with blood transfusions and drugs directed to control blood pressure. The first reported 71-year-old patient remains in stable condition for 16 months without evidence of recurrent active aortic dissection. The second 85-year-old patient remained in stable condition for 28 days, but finally had a second fatal episode of dissection into the left pleural space. The differential diagnosis of nontraumatic left hemorrhagic pleural effusion in an elderly hypertensive patient should include dissecting aneurysm of the descending thoracic aorta and CT of the chest should be performed as the next preferable diagnostic procedure.