Primary mesenchymal neoplasm of the adrenal gland is very rare. Recently we experienced a case of leiomyosarcoma of the adrenal gland in a 47-year-old female patient. The resected adrenal gland showed a large lobulated mass, which replaced the entire gland. The cut surface was firm and whitish gray with foci that showed hemorrhage and necrosis. Histologically, the tumor was composed of intersecting fascicles of pleomorphic spindle cells with numerous giant cells and mitotic figures. Some of the tumor cells showed elongated nuclei. Immunohistochemical studies were strongly positive for vimentin and smooth muscle actin. Cytokeratin, desmin, alpha-1-antitrypsin and lysozyme were all negative. To the best of our knowledge, this is the first case reported in Korea.