Gravitational settling of fine particles in a liquid-filled narrow channel has been studied experimentally and theoretically. Previous studies have shown that the particulate suspension with concentration interface toward gravitational direction behaves as a continuous fluid for high concentration and small particle size, and the gravity-induced instability at the interface enhances the settling motion of particles. The purpose of this study is to investigate how such a concentration interface behaves and how particles settle by gravity in various finite-sized channels. The experimental and theoretical results indicate that the aspect ratio of the channel cross-section is an important parameter for describing the settling behavior of particulate suspension. Moreover, we predict the velocity of the collective settling of particles in channels with arbitrary cross-section. (C) 2013 Elsevier Ltd. All rights reserved.