Morphology of hormonally inactivated pituitary adenoma can be different types of tumors. Morphological immunohistochemical and electron-microscopic researches of 23 hormonally inactivated pituitary adenomas has been carried out. We shown that more frequent morphological substrate was gonadotropinoma or "zero-cells" adenoma. According to our results, gonadotropinomas, "zero-cells" adenomas and oncocytomas have similar features and can be put into the same group of tumor Pathomorphologist has to differentiate this group of tumors from others "silent" pituitary adenomas because they have different prognosis for a disease. A research of somatostatin and dopamine receptors expression would be new area for differential diagnosis of these types of adenomas.