Lumbar disc arthroplasty may be the most innovative and exciting development in the history of spinal surgery. Manufacturers and proponents cite the ability of these devices to relieve pain while preserving motion at the disc space. The preservation of motion is hypothesized to lower the risk of adjacent segment disease and, thereby, improve long-term outcomes. However, the devices are expensive and their use is associated with the potential for significant complications above and beyond those seen with lumbar fusion. At the present time, there is no evidence to suggest that the use of disc arthroplasty results in better short- or long-term functional outcomes than fusion in properly selected patients. Furthermore, there is little if any evidence to support the hypothesis that adjacent segment degeneration is an important clinical entity. Although the absence of proof is not the same as the proof of absence, greater efficacy must be demonstrated to offset the increased costs and complications associated with these devices. Therefore, these devices require further long-term study in a controlled environment before widespread application.