Abstract: A catheter assembly especially designed for the performance of atherectomy procedures which include an elongated flexible plastic tube which can be routed through the vascular system to the location of the atheroma to be removed and a working catheter insertable through the guide catheter in the form of an elongated flexible plastic tube having a series of fibers integrally formed with or otherwise attached to the distal end portion of the working catheter and normally laying flat against the wall of the catheter. The proximal end of the working catheter is adapted for connection to a high speed motor whereby the working catheter can be rotated relative to the surrounding guide catheter.