Objective: With the aid of a 16-mm high-speed movie camera and a Kerr Cell Camera, the authors have investigated how cotton and rayon fibers behave in a running card. Results: Valuable information has been obtained on the air current under the lickerin and under the cylinder-doffer contact. Considerable information has also been obtained on the behavior of fibers on the lickerin, cylinder and doffer, particularly with respect to fiber orientation.