We reviewed 50 cases of gastrointestinal (GI) malignant tumors diagnosed by contrast study combined with gray-scale ultrasonography. Our purpose was to evaluate the diagnostic accuracy of combined methods. Although contrast study remains the chief method for detecting GI tumors, sonography may add information by displaying the internal structure of the neoplasm and the extent of infiltration and metastasis if present. Our sonographic examinations have supplemented the roentgen findings in one way or another indicating that ultrasonography plays an important part in the diagnosis of the GI tumors. We suggest that whenever a GI tumor is revealed by contrast study, gray-scale ultrasound be added in order to make the diagnosis more accurate.