A new microcatheter system was used for diagnostic and therapeutic purposes in three cases of arteriovenous malformation. This microcatheter is used with a steerable guidewire and provides high selectivity of the target vessels and greater catheter maneuverability than does balloon catheters. Tissue adhesive was safely injected for the therapeutic embolization in two of the cases. With this system, however, the utmost attention is necessary to prevent reflux of the tissue adhesive and to avoid lacerating the feeding vessels with the guidewire. This micro-catheter system was found to be very useful for diagnostic and therapeutic procedures in endovascular treatment of cerebral arteriovenous malformations.