Patients with complex or surgically difficult intracranial aneurysms are being treated with interventional neurovascular techniques. With neuroleptic anesthesia and a transfemoral femoral approach, a silicone micro-balloon can be flow directed through the intracranial circulation, guided directly into the aneurysm, and detached. The aneurysm is thus eliminated from the circulation, and the parent artery is preserved. For broad-based or ectatic aneurysms, test occlusion followed by permanent occlusion of the aneurysm and parent vessel can be performed. Since 1981, 211 patients with 215 aneurysms, including 177 cases involving the anterior and 38 cases involving the posterior circulation, have been treated with this technique. In 127 cases (59.1%), the parent vessel was occluded; in 88 cases (40.9%), primary occlusion of the aneurysm was achieved with preservation of the parent artery. Therapy-related complications included 21 deaths (9.8%) and 16 strokes (7.4%). Follow-up examinations were performed at 1, 3, and 12 months after treatment, and follow-up ranged from 5 months to 9 years. In patients in whom standard surgical therapy fails or for aneurysms in surgically inaccessible anatomic locations, interventional techniques that make use of detachable balloons may be a useful therapeutic alternative.