The approach to the management of retroperitoneal tumors begins with a complete history and physical examination. Imaging of the abdomen and pelvis by computed tomography (CT) provides both an imaging modality and a method by which to obtain tissue for diagnosis. Because a histologic diagnosis is essential in treatment planning, adequate tissue can usually be obtained by a CT-guided core biopsy. If the diagnosis is sarcoma, additional tests necessary for staging include plain chest radiography and evaluation of the liver by either CT scan or magnetic resonance imaging (MRI). The treatment options for primary retroperitoneal sarcomas include chemotherapy, radiation therapy, surgery, or a combination of these modalities; therefore, a multidisciplinary group best manages treatment planning. Primary radiation therapy for cure is seldom effective for retroperitoneal sarcomas but can provide palliation in select cases. Systemic chemotherapy for chemosensitive lesions, such as poorly differentiated liposarcoma, malignant fibrous histiocytoma (MFH), synovial cell sarcoma, and primitive neuroectodermal tumors (PNET), can be useful when used in a neoadjuvant manner. Consequently, surgical resection continues to be the mainstay of treatment for retroperitoneal sarcomas and requires en bloc resection of the primary tumor. Frequently this includes adjacent organs such as colon, small bowel, kidney, adrenal, and pancreas. Postoperative adjuvant therapy with chemotherapy or radiation has not been proven to be of any additional benefit. Overall treatment results are predominantly influenced by tumor stage, grade, size, and margins of surgical resection. Follow-up CT scans at 6-month intervals and surgical resection of recurrences can be valuable.