A noncircular inner lumen guiding catheter with assisted variable support has an inner wall defining a noncircular cross-sectional shaped lumen for use in delivery of multiple microcatheters or other devices for treatment of neurovascular defects, such as for treatment of aneurysms. The noncircular inner lumen guiding catheter with assisted variable support includes torque transmittal guidance walls that are flexible linearly but not circumferentially, and that are neither collapsible nor kinkable. The noncircular shaped cross-section of the inner lumen may extend along the entire length of the catheter or a portion thereof, including distal or proximal.