The approach to the sciatic plexus and lateral part of the sacrum is difficult. A subperitoneal anterolateral approach can be extended by sectioning the iliac bone above the acetabulum and lowering it toward the external part of the iliac wing and buttock. This transiliac anterolateral approach exposes the lumbosacral trunk, first sacral foramina and sciatic plexus to the origin of the sciatic trunk. Exposure can be extended upward by subperitoneal lumbotomy, downward by opening the ischiorectal fossa, or outward by trochanterotomy. This approach was used 18 times by one of the authors (FHD) for resection of 13 malignant tumors and 5 plexus releases. Procedure time was 3–6hours, with 500–4,000ml blood loss. The approach systematically enabled surgical objectives to be met. There was 1 septic complication that healed after debridement.