Abstract: It is usually diffecult to distinguish the different types of pituitary adenma only with routine stains and by the light microscopical examination. In our laboratary, 8 of 14 cases of pituitary adenoma have been diagnosied as chromophobe adenoma with light microscopy, while pituitary adenoma with amenorrhea-galactorrhea （Forbes-Albright Syndrome） was diagnosied with electron microscopy in all cases. The electron microscopical study showed a large number of "Nebenkern" composed of aggragation of rough endoplasmic reticulum, prominent Golgi apparatus as well as scarce secretory granules, the last feature being the striking finding in 13 cases.