A 57-year-old man was admitted because of visual disturbance due to a recurrent pituitary adenoma. Nine years ago craniotomy was performed for the chromophobe adenoma and postoperative radiation therapy was applied with tumor dose of 50 Gy. Digital subtraction angiography indicated existence of an aneurysm at the carotid bifurcation and the finding was confirmed by conventional angiography, which revealed a saccular aneurysm and irregularity of the carotid walls. In surgery there were not only the saccular aneurysm found in the angiogram, but also three other fusiform aneurysms and severe sclerotic change at the major arteries adjoining the sellar region. Azzarelli et al. reported a fatal case due to the development of arteriosclerotic intracranial fusiform aneurysms following radiation therapy for suprasellar germinoma. This case is the second case which indicates the development of intracranial aneurysm following radiation therapy. Emphasis is placed on careful follow-up examination for radiated pituitary adenoma with computed tomography, digital subtraction angiography, or occasionally conventional angiography, even though the postoperative condition of the primary lesion is stabilized.