In retrospect, we analyzed 12 cases of gastric smooth muscle tumor, nine cases of leiomyomas and three of leiomyosarcomas. In only half the number of these patients was an adequate preoperative diagnosis made. Ulceration of the tumor apparently led to the misjudgment in some cases. Features more relevant to leiomyosarcoma than to leiomyoma were findings of a larger size, exogastric growth, ulceration and tumor in patients over 50 years of age. It is stressed that enucleation is the treatment of choice for leiomyoma and an extensive gastrectomy for cases of leiomyosarcoma.