METHODS Case report. OBJECTIVE To present a rare case of a giant schwannoma of the cauda equina. BACKGROUND Giant spinal schwannoma of the cauda equina, which involves many nerve roots, is rare and there is usually no ossification in the schwannoma. It is unknown whether or not complete excision is preferable if the tumor is located in the lumbar lesion. METHODS A 57-year-old woman had a 10-year history of low back pain. Scalloping of the posterior surface of the vertebral bodies from L3 to the sacrum was found. Magnetic resonance imaging disclosed a giant cauda equina tumor with multiple cysts. Central ossification revealed by computed tomography and an unusual myelogram made the preoperative diagnosis difficult. RESULTS The patient underwent incomplete removal of the tumor, decompression of cysts, and spinal reconstruction. The tumor was proved to be a schwannoma. The postoperative course was uneventful and she has been almost free from low back pain for 3 years and 4 months. CONCLUSIONS Giant schwannoma in the lumbar spine region is usually excised incompletely, because complete removal had the risk of sacrificing many nerve roots. In spite of the incomplete removal of the tumor, the risk of recurrence is low.