OBJECT: Over the past decade, low-pressure, flow-directed balloons have been replaced by over-the-wire balloons in the treatment of vasospasm induced by subarachnoid hemorrhage (SAH). The authors assess the procedural safety and technical efficacy of these newer devices. METHODS: Seventy-five patients who underwent 85 balloon angioplasty procedures for the treatment of SAH-induced vasospasm were identified from a prospective quality-assurance database. Medical records and angiographic reports were reviewed for evidence of procedural complications and technical efficacy. No vessel rupture or perforation occurred, but thromboembolic complications were noted in four (4.7%) of the 85 procedures. Balloon angioplasty was frequently attempted and successfully accomplished in the distal internal carotid (100%), proximal middle cerebral (94%), vertebral (73%), and basilar (88%) arteries. Severe narrowing was present in 89 proximal anterior cerebral arteries. Angioplasty was attempted in 41 of these vessels and was successful in only 14 (34%). In 19 of the 27 unsuccessful attempts, the balloon could not be advanced over the wire due to severe vasospasm or unfavorable vessel angle. Follow-up angiography in a subset of patients demonstrated that severe recurrent vasospasm occurred in 15 (13%) of 116 vessels studied after angioplasty. CONCLUSIONS: Over-the-wire balloons involve a low risk for vessel rupture. The anterior cerebral artery remains difficult to access and successfully treat with current devices. Further improvements in balloon design, such as smaller inflated diameters and better tracking, are necessary. Finally, thromboembolic complications remain an important concern, and severe vasospasm may recur after balloon angioplasty.