Endosonography (ES) was preoperatively performed in 113 patients with esophageal carcinoma (group 1) and in 84 patients with gastric carcinoma (group 2). Results of imaging and histology of resected specimens were correlated according to the new (1987) TNM classification. ES was accurate in assessing the depth of tumor infiltration. Overall accuracy of ES for group 1 was 89% and for group 2 83%. Early carcinomas could be distinguished from advanced cancers. ES was accurate in diagnosing lymph node metastases (sensitivity group 1 95% and group 2 87%) but less accurate in defining inflammatory changes of lymph nodes (specificity group 1 50% and group 2 48%). The incidence of lymph node metastases increased with progression of the depth of tumor infiltration. ES is not accurate for staging distant metastasis due to the limited penetration depth of ultrasound. Thus, additional transcutaneous ultrasound or computed tomography is necessary. Routine ES-guided cytology of lymph nodes may further enhance the diagnostic accuracy of ES.