Abstract: Objective:To retrospectively investigate the regulation of cervical and posterior to level V (PLV) lymph node metastasis on clinical target delineation in radiotherapy for nasopharyngeal carcinoma (NPC).Methods:A total of 428 NPC cases from February2013 to April2016were subjected to enhanced CT scan from the base of the skull to the clavicle for pathological diagnosis. A deputy chief physician and an attending physician assessed the nodal distribution in each level in accordance with the RTOG guidelines proposed in 2013. The central point of the metastatic lymph nodes of PLV in the patients were recreated proportionally on the CT images of a stan -dard patient with N0 NPC in reference to the normal anatomy of the PLV area. SPSS 19. 0 was used to analyze the correlation between PLV and the other levels. Moreover, the nodal location and characteristics of PLV were analyzed.Results:Among the 428 patients, 381 (89. 0% ) showed nodal involvement. The top four metastatic probabilities were presented as follows: Ⅱb (75. 2% ),Ⅶa (60. 3% ),Ⅱa (59. 6%), andⅢ(42. 0%). Up to 21(4. 9%) patients exhibited nodal involvement of PLV with32nodes. The mean vertical distance of all central points of PLV from the anterior border of the trapezius was16mm. Correlation analysis indicated the nodal involvement of PLV with the ipsilateral level Va ( P=0. 001 ). Conclusion: NPC showed a high probability of nodal metastasis. Nodes were mostly metasta-sized from the upper to the lower level, as well as from the proximal to the distal area. The leap metastasis rate was very low. The nod -al involvement of PLV correlated with the ipsilateral metastasis of level Va. Thus, the ipsilateral delineation of the posterior border of level V should be contoured to 25mm far from the anterior surface of the trapezius during the nodal involvement of level Va.