TO MONITOR THE course of infectious intracranial aneurysms, repeated cerebral angiography has been recommended every 2 weeks during intravenous antibiotic therapy until the aneurysm has resolved or an operation has been performed. However, serial cerebral angiograms are not without some risk to the patient. We have prospectively studied five patients harboring a total of six infectious intracranial aneurysms by sequential computed tomography (CT) and/or magnetic resonance imaging (MRI) studies. All infectious aneurysms were initially identified by cerebral angiography and were treated with 6 to 8 weeks of intravenous antibiotics. The aneurysm size ranged from 4 to 10 mm. Sequential CT scans and/or MRI studies were obtained at 2- to 3-week intervals to monitor the course of the aneurysms. Three aneurysms enlarged during antibiotic therapy, and one remained unchanged in size. These four aneurysms were treated surgically. The two remaining aneurysms resolved with intravenous antibiotic therapy. Cerebral angiograms were obtained routinely preoperatively and were used to verify the resolution of the infectious aneurysms when they were no longer visible on CT or MRI. On the basis of this prospective study, we conclude that sequential thin-slice CT and/or MRI can effectively and safely monitor the course of infectious intracranial aneurysms once identified by cerebral angiography. This may reduce the need for serial angiography and reduce the ultimate risk in the management of infectious intracranial aneurysms.