64 patients (38 with esophageal and 26 with gastric carcinoma) underwent a preoperative endosonography. In 21 patients with esophageal tumors and in 24 patients with gastric tumors a complete endosonographic examination was performed. In 16 of 21 patients (76%) with esophageal carcinoma the tumor infiltration (T-stage), and in 16 of 18 cases (89%) the lymph node metastases (N-stage) could be assessed accurately. The depth of infiltration of cardia and gastric carcinoma was recognized in 15 of 19 cases (79%), and in 13 of 18 patients (72%) the N-stage was evaluated. Endosonography represents a method which can accurately predict tumor infiltration and regional lymph node metastases.