We investigated the long-term functional outcome of patients with suprasellar germinoma after radiotherapy to determine the usefulness and limitations of radiotherapy for these tumors. From among 54 cases of intracranial germ cell tumor at Kitasato University Hospital, 12 patients with suprasellar germinoma who were treated with radiotherapy but not chemotherapy retrospectively investigated for mental, hormonal and visual functions. The follow-up period ranged from 63 to 262 months (mean, 161.1 months). The mortality rate was zero and there was no recurrence of tumors. However, three patients treated with local irradiation alone showed metastasis to the ventricles or spinal cord. With regard to mental function, 50% of the patients showed remarkably low mental function after radiotherapy. With regard to pituitary hormonal function, deficiency of ADH, GH, ACTH, and TSH was documented in 75%, 41.7%, 16.7% and 8.3% of the patients, respectively, before radiotherapy. Prolactin was elevated in 50% of the patients. After radiotherapy, 91.7% needed hormone replacement. With regard to visual function, most patients showed an improvement or no change after radiotherapy. In conclusion, radiotherapy for suprasellar germinomas gave long-time survival. However, such radiotherapy may cause mental and pituitary hormonal dysfunction. Our results show that while radiotherapy is useful for treating suprasellar germinomas, its dose have some limitations.