Lugol stain for intraoperative determination of the proximal surgical margin of the esophagus. An adequate proximal surgical margin is difficult to determine particularly in cases of esophageal carcinoma with surrounding intraepithelial invasion. We report here readily facilitated intraoperative approaches for detection of the exact margin of carcinomatous invasion of the esophagus. The resected specimen of the esophagus is incised longitudinally and placed in a 1% Lugol bath for 2-3 minutes. The normal squamous epithelium includes glycogen that interacts with the iodine of Lugol's solution and the normal epithelium of the esophagus becomes a uniform greenish-brown. A squamous cell carcinoma does not include glycogen, hence is not stained with this solution and a clear identification is feasible. Thus, a carcinomatous infiltration not recognizable in routine examinations becomes macroscopically visible when Lugol's solution is used. 