Idiopathic aneurysm of the inferior vena cava is rare. Many aneurysms are asymptomatic; others are diagnosed after complications develop. Ganglioneuroma is an infrequently occurring benign tumor preferentially located in the mediastinum and retroperitoneum. Generally the clinical manifestations are symptoms of compression related to growth of the mass. We present a case report of idiopathic aneurysm of the inferior vena cava associated with retroperitoneal ganglioneuroma. The tumor was resected in combination with a procedure to correct the aneurysm that has not previously been described, ie, tangential resection and primary lateral venorrhaphy. The technique provided excellent short-term results.