STUDY DESIGN: Clinical radiographic and outcomes investigation. OBJECTIVE: To investigate clinical and radiographic outcomes for lumbosacral fusion (in patients with spinal deformity) using a combination of bilateral sacral and iliac screws with a minimum 5-year follow-up. SUMMARY OF BACKGROUND DATA: To our knowledge, long-term results (>5 years of follow-up) of bilateral S1 screw/bilateral iliac screw fixation have never been published or presented. MATERIALS AND METHODS: A total of 67 patients (from an initial consecutive cohort of 81) undergoing lumbosacral fusion with bilateral sacral and iliac screws with a minimum follow-up of 5 years (range 5-10 + 5, average 6 + 3) were analyzed for radiographic outcome and clinical course by an outcome questionnaire (administered at ultimate follow-up) analysis. Patients were divided into 2 groups: group 1, 34 patients with mostly high-grade spondylolisthesis; and group 2, 33 with adult scoliosis fused mostly from the thoracic spine to the sacrum. A true anteroposterior pelvis film was obtained in all patients to assess for sacroiliac joint arthritis, as were standard spine radiographs. Patients were administered Oswestry and directed buttock pain questionnaires at latest follow-up. RESULTS: There were no cases of sacral screw failure (i.e., screw loosening, partial screw pullout, or fracture of the sacral screw). There were 5 cases of nonunion at L5-S1. Of the 5 cases, 3 did not have anterior column support at L5-S1. Four of the 5 cases were revised, and, subsequently, 3 achieved union. Iliac screws were removed electively on 1 or both sides in 23 of the patients after 2 years postoperatively because of prominence. There were 7 cases of iliac screw breakage. Iliac screw halos were observed in 29 patients. No sacroiliac osteoarthritis was observed on the true anteroposterior pelvis films. At ultimate follow-up, average visual analog painscale (0-10) score to assess buttock pain was 2.4, and average Oswestry score was 20.1. CONCLUSIONS: For high-grade spondylolisthesis and long adult deformity fusions to the sacrum, a montage of bilateral S1 screws and iliac screws were effective in protecting the sacral screws from failure. Pseudarthrosis at L5-S1 was manifested by rod breakage at that level. We saw no evidence of a long-term effect of the iliac screws predisposing the sacroiliac joints to degeneration at follow-up ranging from 5 to 10 years.