Two cases of symmetrical uterine enlargement, with widespread involvement of the myometrium by innumerable leiomyomata, mainly of small and microscopic size, are reported. This unusual leiomyomatous enlargement of the uterus precludes myomectomy. A review of the literature revealed only 3 previous cases of this condition. The designation of diffuse leiomyomatosis of the uterus is proposed. The pathogenesis and differential diagnosis are discussed.