Clinical pathologic observation and immunohistochemical demonstration on beta--HCG are reported in 13 cases of intracranial primary germinomas, including 7 cases of germinomas in the region of the pineal gland and 6 cases in the hypothalamic area. Among them, there were 11 cases of simple type and 2 cases of beta--HCG--producing tumors with a character of differentiation of trophoblasts in the latter. This paper supports the concept that intracranial primary germinoma is an atypical teratoma arising from the germ cells. The significance of beta--HCG immunohistochemical demonstration in the pathologic diagnosis of germinomas and the mechanism of endocrine disturbance are discussed.