Two cases of gastric leiomyosarcoma diagnosed by ultrasound are presented. Upper abdominal sonogram disclosed a large lobulated echogenic mass containing a few or multiple anechoic fluid-filled spaces in each cases. These anechoic spaces were confirmed to be necrotic or hemorrhagic cavities in the solid mass pathologically. The authors wish to emphasize these echopatterns are characteristic of mesenchymal tumor, such as leiomyoma or leiomyo-sarcoma, in particular.