The invention of pedicle screw instrumentation has greatly improved outcomes of spinal fusion, which has become the treatment of choice for lumbar spondylolisthesis. As researchers accumulate experience, both theoretical and clinical advances are continually being reported. A review of the literature and the experience of the authors show that the development of adjacent instability, as in the breakdown of a neighboring unfixed motion segment, is a common consequence of an instrumented lumbar spine. This article reviews the risk factors and surgical treatment of adjacent instability. The authors believe that proper preoperative planning and complete surgical procedures are imperative to prevent adjacent instability. For those who need revision surgery, meticulous surgical techniques can achieve satisfactory results.