Brain scan with 99mTc-labelled macroaggregated albumin (MAA brain scan) and computed tomography studies (CT) were performed on 78 patients with intracranial diseases. 99mTc-MAA was injected into right and left carotid artery respectively, at the different time. And then diagnostic evaluation of both techniques were investigated. The MAA brain scan was useful for the detection of ischemic lesion in the early stage after onset of cerebral infarction. It was shown in 29.5% that partial field of anterior cerebral artery was injected through the contralateral artery. In these cases, the MAA brain scan was also useful. In the cases of hemorrhagic lesions, however, the CT was more useful than MAA brain scan. Therefore, the both techniques helped each other in the diagnosis of intracranial diseases.