Although our experience to date indicates that stereotactic thrombosis of intracranial aneurysms with a magnetic probe is a safe and effective procedure for patients with aneurysms of the anterior communicating artery which are less than 1 cm in diameter, additional improvements have been made to increase the safety of the procedure. It has been demonstrated that monitoring the pressure within the injection needle will insure that the needle is within the aneurysm before any iron is injected. Increasing the size of the magnetic probe and inserting coiled iron wire into the aneurysm will enhance the thrombosis of large aneurysms. Studies are still in progress on better methods for monitoring the progression of aneurysm thrombosis. One of the major advantages of the magnetic technique is that the aneurysmal fundus is punctured at the opposite pole from the aneurysmal neck. This may account for the absence of vasospasm seen in our cases as compared to the significant vasospasm reported with the electric thrombosis technique. The modifications described herein have not altered this principle.