BACKGROUND CONTEXT Adjacent segment pathology (ASP) continues to be a concern for surgeons and patients following cervical spine surgery. Most reports to date have focused on either reoperation at the index level or reoperation at any level. There is little debate that radiographic ASP (rASP) favors cervical disc arthroplasty (CDA), but few studies have explored clinical ASP (cASP). PURPOSE To evaluate cASP in patients treated with CDA or ACDF. STUDY DESIGN/SETTING Post-hoc analyses were performed on data that was collected through 7years in a prospective, randomized, controlled clinical trial comparing CDA to ACDF with allograft and anterior plate at one or two contiguous levels. PATIENT SAMPLE The patient population consisted of 575 randomized patients: 164 one-level CDA and 81 one-level ACDF; 225 two-level CDA and 105 two-level ACDF. OUTCOME MEASURES Adjacent level surgeries through 7years. METHODS Kaplan-Meier survival curves for adjacent level surgery were compared using the log-rank test. Cox regression was used to assess the impact of treatment on the relative risk of adjacent level surgery. RESULTS Follow-up rates through 7years were 74.6%. The proportion of patients undergoing an adjacent level surgery was 14.8% for 1-level ACDF, 4.3% for 1-level CDA, 12.4% for 2-level ACDF, and 4.9% for two-level CDA. Kaplan–Meier survival estimates of the probability of adjacent level surgery heavily favored CDA over ACDF (p CONCLUSIONS The adjacent level surgery rates of ACDF patients are over three times higher than CDA at one-level and 2.5times for two-level through 7-years follow-up. In this patient population the survival estimates strongly favor CDA, with estimated rates of adjacent level surgery per 100 patients three times higher for ACDF (p