An ultra-thin-walled 4-French catheter was used for angiography and as a guiding catheter for the Tracker-18 microcatheter in patients with intracranial dural arteriovenous fistulas (AVFs), spinal dural AVFs, spinal epidural AVF, meningioma, and acute embolic occlusion of major cerebral vessels. The 4-French guiding catheter was introduced through the transfemoral or transbrachial route. The guiding catheter and the guidewire were advanced to the aortic arch and then turned over just above the aortic valves, and finally the catheter was introduced into the external carotid artery or vertebral artery when the transbrachial approach was selected. Images of the intracranial vessels and spinal dural branches obtained were excellent in all cases. The Tracker-18 could smoothly be advanced to the target artery through the 4-French catheter in all patients. Endovascular treatment with the Tracker-18 can be performed using an ultra-thin 4-French guiding catheter, and safely via the transbrachial route.