We present the results of a cooperative study of 15 cases of suprasellar dysgerminomas (ectopic pinealomas) and a review of cases of the literature with histological confirmation. In all the cases, histological similarities to the germinomas which appear extracerebrally, particularly testicular seminomas, were observed. We were unable to find in the sellar region tumors of true pineal histology and tend therefore to confirm the germinal origin of these neoplasms. From a clinical point of view, we define a syndrome that these tumors produce, consisting of diabetes insipidus as the first sign, visual impairment and endocrine disturbances, with few or no radiological signs in plain studies.