The rate of progression of cervical ossification of the posterior longitudinal ligament (OPLL) was radiologically studied during a 3-year period in three patient populations: (a) after laminoplasty (25 patients), (b) after laminectomy (16 patients), and (c) in patients who were managed without surgery (56 patients). There appeared to be no significant difference between these two surgical procedures in postoperative progression of OPLL. When progression of OPLL was compared between patients treated surgically and nonsurgically, posterior surgery accelerated progression of OPLL.