During the last 5 years, the concept of sentinel lymph nodes has been investigated in a variety of solid tumors. Despite the multidirectional and complex lymphatic drainage of the stomach, early gastric cancer has been shown to be a suitable model for sentinel lymph node mapping. In contrast, sentinel lymph node mapping of esophageal cancer is compromised by the anatomic location of the esophagus and its lymphatic drainage in the closed space of the mediastinum. The technique and clinical application of sentinel lymph node mapping thus differ between esophageal and gastric cancer. Reliable detection of sentinel lymph nodes in the mediastinum requires radioisotope labelling, while blue dye and radioisotope labelling are both feasible for gastric cancer. In patients with early gastric cancer, laparoscopic resection with sentinel node negative status is already under investigation in clinical trials. In esophageal cancer, sentinel node mapping is still considered an experimental technique. Preliminary data, however, indicate that it may be reliable and feasible in patients with early adenocarcinoma of the distal esophagus.