A case of malacoplakia involving the urinary bladder and appendiceal peritoneum in a 69 years old female was studied by light and electron microscopy. Light microscopic features were characteristic of classical description, namely massive infiltration of macrophages with large amount of clear cytoplasm numerous PAS positive granules and Michaelis-Gutmann bodies. On electron microscopy, many colliform bacterial structures were noted in the cytoplasm phagosome and phagolysosome of macrophages. Although no transitional stages from phagolysosome into Michaelis-Gutmann body were observed st our study, the presence of bacilli in cytoplasm and phagolysosome strongly supports the Michaelis-Gutmann body is formed by calcification of phagolysosome which engulfed bacilli.