Microscopically assisted posterior lumbar interbody fusion was performed on 27 patients who had either spondylolisthesis or chronic lower back pain after previous lower back surgery. Overall improved satisfactory results occurred in 22 of 27 patients. Roentgenographic, stable, interbody fusion occurred in 22 of 27 patients. The poorest results and highest rate of pseudarthrosis occurred in patients with double-level fusions. Pseudarthrosis occurred in four of six patients with double-level fusions and unsatisfactory clinical results occurred in five of six patients with double-level fusions. Advantages of the microscopic technique are better examination of the surgical site, less blood loss, and less surgical dissection than other surgical salvage techniques. This procedure should be reserved for single-level pathology in the lumbosacral spine.