Cervical ossification of posterior longitudinal ligament (OPLL) can cause cord compression which can lead to myelopathy. Operative management including anterior fusion or laminoplasty is needed in these cases. Understanding the progression course of OPLL, risk factors of progression, and risk factors of myelopathy caused by OPLL is essential to determine the necessity, timing and method of operation. Therefore, we will review the previous study results regarding characteristics and progression course of OPLL. Furthermore, the results of study about risk factors and progression course of OPLL undergoing conservative management will be discussed.