OBJECTIVE: The purpose of this study is to compare the efficacy and safety of anterior cervical discectomy and fusion (ACDF) and cervical total disc replacement (CTDR) as revision surgeries for symptomatic adjacent segment degeneration (ASD) in cases with previous ACDF. PATIENTS AND METHODS: Between 2010 and 2014, 41 patients with previous cervical fusion surgery underwent ACDF or CTDR for symptomatic ASD. Twenty-two patients in the ACDF group underwent 26 ACDFs, and 19 patients in the CTDR group underwent 25 arthroplasties for symptomatic ASD. Clinical outcomes were assessed by a visual analogue scale (VAS) for arm pain, the neck disability index (NDI) and Odom's criteria. Radiological evaluations were performed preoperatively and postoperatively to measure changes in the range of motion (ROM) of the cervical spine and adjacent segments and arthroplasty level. The radiological change of ASD was assessed in radiographs. RESULTS: Clinical outcomes as assessed with VAS for arm pain and Odom's criteria were significantly improved in both groups. The CTDR group showed better NDI improvement after surgery (P<0.05). The mean C2-7 ROM of the CTDR group revealed faster recovery than did that of the ACDF group and the preoperative values were recovered at the last follow-up visit. There was a significant difference in the ROM of the inferior adjacent segment between the ACDF and CTDR groups (P<0.05). The ACDF group had a higher incidence of radiological changes in the adjacent segment compared with the CTDR group (P<0.05). CONCLUSIONS: The 2-year clinical results of CTDR for symptomatic ASD are safe and are comparable to the outcomes of ACDF in terms of arm pain relief and functional recovery. The CTDR group showed better NDI improvement, faster C2-7 ROM recovery, less of an increase in ROM in the inferior adjacent segment, and a lower incidence of adjacent segment degeneration than did the ACDF group.