With the use of a linear scan type ultrasonic endoscope, the possibility of gastric fiberscopy with ultrasonic procedure in the estimation of the extent of deep infiltration of gastric cancer and in the transgastric diagnosis of pancreatic tumors was studied. Results revealed that the echogenicity of the tumor was more clearly recorded by ultrasonic endoscopy than routine ultrasonography taken via the abdominal wall. With improvements in both the probe and manipulation technique, the device is expected to achieve far-reaching contributions to the diagnosis of the deep invasion of gastric cancer and small-sized pancreatic tumors.