The authors present clinical and morphological characteristics of gastric leiomyoblastoma (25 cases) nominated by Soviet investigators as a myoid or angioleiomyomatous variant of a glomus tumor. The tumor was composed of leiomyomatous sites, clusters of epithelioid cells with apparently empty cytoplasm and frequently odd nuclei. Morphological criteria are suggested referring leiomyoblastoma to mature, infiltrative and malignant. Electron-microscopic examination in 8 cases provided evidence for myogenic origin of the neoplasm. Smooth muscle differentiation is shown to resolve with growing of cell proliferation and relevant atypia.