An atherectomy catheter for removal of plaque buildup from the walls of a blood vessel. The atherectomy catheter includes a cutter assembly disposed at the distal end of a flexible guide tube that may be inserted into a vessel and directed to the occlusion. A proximal actuator assembly is adapted to impart both rotary and axial movement to the cutter. The cutter assembly includes a cutter having a forwardly extending annular cutting surface. A guide wire with a flexible spring tip extends forward of the cutter for guiding the cutter as it travels axially through the artery. All of the removed atheroma materials are collected within the device and a retention member carried by the guide wire and positioned in front of the cutter forms a cap to retain the collected atheroma materials. In a disclosed embodiment, the retention member is expandable, and in one of the preferred embodiments, the retention member may be expanded to engage the vessel walls to anchor the device during the cutting stroke.