In quest of an endarterial treatment for intracranial arteriovenous malformations and fistulas, a microcatheter which can be flow-guided into third- and fourth-order branches of the intracranial arteries was developed. This permits controlled deposition of a vascular occlusive polymer (isobutyl-2 cyanoacrylate). Goals and experimental techniques are reviewed and clinical experience on the first 25 patients is presented. Complications included one stroke and three catheters glued in place, but refinements in technique have permitted avoidance of complications over the 14 months before this report.