&NA;A pseudoaneurysm of the inferior gluteal artery presenting as sciatic nerve compression is reported in a 40‐year‐old woman. Following a transvaginal needle biopsy for endometriosis, the patient developed left sciatic pain and a nonpulsatile mass palpable in the left buttock thought to represent a pyriformis hematoma. Sequential computed tomographic scans were consistent with this diagnosis. Persistent pain and progression of neurological deficits led to surgical exploration. Posterior exposure of the pyriformis muscle and proximal sciatic nerve revealed a large pseudoaneurysm of the inferior gluteal artery compressing the nerve. A laparotomy was performed and the internal iliac artery was ligated, followed by evacuation of the aneurysm contents and repair of the aneurysm neck via a posterior approach. The patient has remained pain‐free with progressive improvement in neurological function after 1 year follow‐up. Aneurysms of the gluteal artery are unusual, predominantly occur after significant pelvic trauma, and rarely present as sciatica. Pertinent aspects of the patient history and clinical findings are atypical for discogenic sciatica. Because of the rarity of this entity, preoperative diagnosis is usually not achieved. Angiography or magnetic resonance imaging should be performed in patients with atypical sciatica and a mass in the region of the proximal sciatic nerve, particularly after trauma. (Neurosurgery24:926‐928, 1989)