A patient developed the superior vena cava syndrome from Nocardia asteroides pneumonia with mediastinitis. Specific treatment was dangerously delayed because malignancy was primarily suspected, and nocardial infection was not initially considered. The correct diagnosis was eventually made by appropriate stains and culture of a lung aspirate. Specific therapy with sulfonamide resulted in a cure of the infection, disappearance of facial swelling, and a long-term state of clinical well-being. Active nocardial pneumonia with mediastinitis is a treatable cause of the superior vena cava syndrome and should be considered in the differential diagnosis.