Under the electronmicroscope we observed a case of an acinic cell tumor of the left parotid gland. The patient was a 63-year-old woman who has suffered three times from local recurrences. The cytoplasma of the tumor cells showed the well-organized mitochondria, rouch endoplasmic reticula, Golgi's complexes and other organellas. Especially the cytoplasmas of the tumor cells, which formed acinus-like lumens, contained various-shaped secretory granules in great numbers. In addition, pycnotic-nucleated oncocytes with secretory granules could be observed.