Endosonography (ES) was preoperatively performed in 91 patients with esophageal carcinoma and 80 with gastric carcinoma. Imaging findings were correlated with those from histologic analysis of resected specimens. ES was accurate in assessment of the depth of tumor infiltration. Early-stage disease could be distinguished from advanced carcinoma. Overall accuracy of ES was 90% for assessment of esophageal carcinoma and 83% for gastric carcinoma. Stenosis was a limiting factor for accurate staging (16% of cases). ES was reasonably accurate in assessment of lymph node metastasis: Overall accuracy was 82% for the esophagus and 66% for the stomach. For nonmetastatic lymph nodes, however, the accuracy was low (56% or less for both esophagus and stomach). Difficulties occurred in distinguishing inflammation from micrometastatic lymph node involvement. ES was not accurate for diagnosis of distant metastases due to limited penetration of ultrasound. Prevalence of lymph node metastasis increased with the progression of tumor infiltration. Technical improvements, such as a smaller diameter echoprobe, may further enhance diagnostic accuracy of ES.