The first 50 consecutive patients stabilized with Cotrel-Dubousset rods for lumbar or lumbosacral fusions were followed for an average of 2 years. The occurrence of fusion, maintenance of alignment, and rate of hardware complication were examined. There were 28 men and 22 women, ages 18–87 years, and 133 vertebral levels. Twenty-nine sets of 5-mm, and 21 pairs of 7-mm, rods were placed. Two hundred and sixty-eight pedicle screws were used. Forty-eight out of 50 (96%) patients demonstrated successful arthrodesis after their initial procedure. One pedicle screw became separated from the rod. No rods migrated or broke. Seven (2.6%) pedicle screws bent and 3 (1%) broke. Large and small diameter Cotrel-Dubousset rods allowed short segment lumbar and lumbosacral fusion with a high degree of reliability.