We have scanned 99 patients of gastric cancer by the 7.5 MHz electrical linear probe, Toshiba SAL-77A and Toshiba-Machida EPE 703FL. We compared the ultrasonic images with the histopathological findings. The echo level of ultrasonic images is graded to 64 degrees. We calculated the echo level from the histogram obtained by the accessory function of the apparatus. We set the mean echo level of the third hyperechoic layer to the 32 degrees by adjusting the distance between the probe and the object, and the main gain control. The ultrasonic images of the gastric wall are consist of three hyper-echoic layers and two hypo-echoic layers between them. By comparison of the ultrasonic images with the pathological findings, we concluded that each layer of them corresponds to foveolar epithelium, mucosa propria, submucosa, muscularis propria, subserosa and serosa respectively. The mean echo level of the second hypo-echoic layer (mucosa propria) and the forth hypo-echoic layer (muscularis propria) are 15 and 10 degrees respectively. The mean echo level of the gastric cancer mass and the ulcer scar in the layer of submucosa are 15 and 22 degrees respectively. We consider that it is reasonable to evaluate the echo level of gastric cancers by comparing it with that of normal mucosa (the second hypo-echoic layer). The 81% of the cases were diagnosed correctly as early gastric cancer preoperatively by means of ultrasonic endoscope. We conclude that it is very useful to evaluate the depth of gastric cancer invasion using ultrasonic apparatus preoperatively.