Abstract: To evaluate the results of highfrequency ultrasound in the diagnosis of residual lymph nodes and to provide a basis for the further treatment of nasopharyngeal carcinoma after radiotherapy. MethodsAfter 90 patients with nasopharyngeal carcinoma accepted radiotherapy, 64 residual lymph nodes were found by highfrequency ultrasound and compared with pathologic biopsy. The patients were divided into the residual group and the no residual group. The characteristics in ultrasound were analyzed which included the long diameter, the short diameter, the echogenic of the hilus and the mode of vascular distribution in the lymph node. ResultsIn the residual group, ultrasound examination showed the diameter in the long direction was significantly bigger than that of the no residual group, the vascular speeds in the lymph nodes were much quicker and vessel modes were mainly in type 3 and 4, and the echogenic hilus was distorted or lost. There were significant differences between the two groups in the above mentioned indicators(all P＜0.01). ConclusionHighfrequency ultrasound plays an important role in evaluating the effect of radiotherapy in the treatment of nasopharyngeal carcinoma. It can be used as an ordinary method to look for residual lymph nodes in nasopharyngeal carcinoma after radiotherapy.