Abstract: To investigate the appropriate margins of clinical target volume ( CTV ) in the supraclavicular region for postoperative radiotherapy of patients with esophageal carcinoma. Methods: Recurrence of esophageal cancer in supraclavicular nodes after radical esophagectomy with two-field lymphadenectomy was retrospectively reviewed, and the relative position, including the recurrent distance ( D ) from the center of metastasized supraclavicular nodes to the body-midline, was measured. The superior border of the lymph node in the axial CT images was recorded. Results: Data from 66 patients with supraclavicular nodal recurrence after surgery were included in the present study. A total of 76 recurrent lymph nodes, with an average size of ( 2.05±1.02 ) × ( 1.55±0.73 ) cm in the supraclavicular region, were assessed. D was ( 1.77±1.19 ) cm ( range 0–5.4 cm ). The upper limit of 95% reference range for D in all patients was 5.05 cm. Aside from the relapsed nodes in the supraclavicular region ( below the level of the arch of the cricoid cartilage ), 5 more recurrent jugular nodes were also collected ( above the arch of the cricoid cartilage ). A total of 4.5% ( 3/67 ) of all the patients had a recurrence above the arch of cricoid cartilage. Conclusion: The inclusion of the outmost lymphatic drainage area of the transverse carotid artery is unnecessary when determining the CTV for the postoperative prophylactic radiotherapy of thoracic esophageal carcinoma in the supraclavicular region. A CTV exterior margin of 6 cm away from the body-midline is suitable for the treatment, and only irradiating the arch of cricoid cartilage or the supraclavicular region below the cricothyroid membrane is reasonable.