Review article of current knowledge of disc arthroplasty.To review the rationale for disc replacement, the general principles of design, and early clinical results.Disc arthroplasty is an emerging treatment for patients with disc degeneration. Its theoretical advantages are to maintain motion, decrease the incidence of adjacent segment degeneration, avoid complications related to fusion, and allow early return to function.Literature review of currently implanted prostheses or those undergoing investigation.At this time, the theoretical advantages are unproven clinically but have been confirmed in biomechanical and kinematic investigations. Multicenter studies of both cervical and lumbar prostheses have shown short-term results equivalent to fusion. Neurologic complications and failures have been rare. Prosthetic subsidence and long-term wear will most likely be potential failure mechanisms. Thus far, with the exception of nucleoplasty, these problems have not been observed.The early results are satisfactory, but the basic premise that motion preservation will diminish adjacent segment degeneration is yet unproven. Long-term results are unavailable and failure modes are unknown. Before implantation, the surgeon and patient must understand the experimental nature of the devices.