In order to clarify the motion of fibers in Newtonian and non-Newtonian fluids, the free falling behavior of a group of cylindrical slender bodies was experimentally investigated in stationary water and polymeric fluids by means of continuous photographing technique using a motor drive-equipped camera, and an analysis method was developed to evaluate the actual motion of the slender bodies. In this paper, interferential effect between the bodies on the falling behavior was reported in detail. Furthermore, the difference between the motion in Newtonian and non-Newtonian fluids was interpreted by comparing the results in water and polymeric fluids. Main findings obtained from this study can be summarized as follows : (1) In whatever fluid, water or polymeric fluids, the slender bodies perform an interferential motion with changing momentarily their mutual attitudes. (2) In water, no slender body behaves independently free from the interference of other bodies, and the pattern approaching to a horizontal direction with damped oscillation takes place frequently. (3) In polymeric fluids, most of the slender bodies show an independent falling behavior at the beginning of their motion. However, the degree of interference between the bodies becomes greatly increased as the motion is continued. (4) In the more concentrated polymer solutions, interferential effect decreases because the flow region occurring due to the motion of the slender bodies becomes smaller.