Lymphoscintigraphies of esophageal carcinoma in nine patients were studied with the aid of 99mTc-labeled rhenium sulfur colloid (99mTc-Re). 99mTc-Re was injected into the submucosal layer of the esophagus (just above the oral side of the tumor) using an esophagoscope, 1 or 2 days before operation. Lymphoscintigraphies at intervals of 1, 3 and 20 h after the injection were performed. After that, the region and the number of the visualized (hot) nodes were assessed. After the operation the lymph nodes were dissected and the hot nodes were determined by scintiphotography. The dissected nodes were then studied histologically. A total of 106 nodes were removed from the mediastinum of nine patients. Histologically, metastases were found in 12 of 106 nodes. Twenty six of 106 (24.5%) could be observed visually on the scintigram and 80 (75.5%) could not. Among the visualized (hot) nodes, 34.6% were positive for metastasis. On the other hand, among the nonvisualized, so-called cold, nodes, only 3.8% were positive for metastasis. Hot nodes of the esophagus indicate a high percentage probability of metastatic nodes.