We report a case of intra-cranial aneurysm of the left cavernous internal carotid artery occurring 27 years after radiotherapy of the pterygopalatine fossa for Hodgkin disease. The development of the aneurysm within the irradiation field, the long latency after radiotherapy, the normality of carotid angiography before radiotherapy and the absence of other etiologies led to the diagnosis of radiation-induced aneurysm. The main characteristics of radiation-induced intra-cranial aneurysms are reviewed.