The management and screening of unruptured asymptomatic intracranial aneurysm (ICA) in patients with ADPKD and those with a family history of ICA remains a subject of considerable controversy. In recent years, it has been revealed that MRA (magnetic resonance angiography) can define the circle of Willis to allow detection of ICA as small as 3-4 mm. We report a case of a 63-year-old man with ADPKD and his family. No definite aneurysm was observed by angiography screening at 46 years of age, when he was referred for hemodialysis. For the past three years, his family history revealed that three relatives were suffering from subarachnoid hemorrhage at the ages of 32, 36 and 39 years, respectively, two of whom had ICA and one had arterio-venous malformation detected by angiography. Whether they had ADPKD was unknown, but two were suggestive of ADPKD. Therefore, our case underwent MRA as screening for ICA, which showed an ICA with a diameter of 5mm in the anterior communicating artery. The ICA was confirmed as being 6 mm in diameter by conventional angiography. His niece and her son, who had ADPKD, also underwent MRA, which showed a suspicious image of a 2 mm ICA in the latter case. These results suggest that prophylactic screening for ICA is important in an ICA clustering family. MRA is useful in screening for ICA and in the follow-up study on the natural course of ICA.