Background and Objectives：Second primary esophageal cancer has been reported to comprise 6-9% of head and neck cancer cases, which are frequently detected in the advanced stage. Thus, detecting esophageal cancer in the early stage is im-portant in the prognosis of head and neck cancer. However, it is difficult to detect early lesions using the conventional endoscopy. In the current study, the feasibility of endoscopic screening using Lugol's solution was assessing for detecting early esophageal cancer in patients of head and neck cancer. Subjects and Method：Sixty-two patients (Group I-synchronous cancer study group) diagnosed with head and neck cancer between November, 2003 and November, 2004 were prospectively studied. Forty-six patients (Group II-metachronous cancer study group) under the follow-up care with head and neck cancer during the same period were also evaluated. The esophagus was initially observed under direct endoscopic view and then Lugol dye was sprayed at the esophagus. Any unstained area was biopsied. Results：Of 34 patients (54.8%) with unstained lesions in Group I, 10 (16.1%) showed dysplasia and 4 (6.4%) had cancer. Of 21 patients (45.6%) with unstained lesions in Group II, 2 (4.3%) showed dysplasia and 5 (10.8%) had cancer. Among 9 (8.3%) second primary esophageal cancer, 6 were detected with super-ficial esophageal cancer while the other 3 were found to be in the advanced stage of cancer. This superficial cancer revealed non-specific mucosal findings in the direct endoscopic view and was difficult to be visualized as a pathologic lesion; however, it revealed unstained areas when Lugol's solution was sprayed, thus could be diagnosed as cancer through biopsy of the area. Conclusion：Endoscopy of esophagus with Lugol's solution could be highly effective as a screening method to detect second primary esophageal cancer in patients with head and neck cancer. (Korean J Otolaryngol 2006;49:1008-13) KEY WORDS：Head and neck cancer·Second primary·Lugol's solution.