In the following paper, a brief summary is first of all given of the results and interpretation of tests already made known in former publications of the Laboratory for Hydraulic Research and Soil Mechanics at the Federal Institute of Technology, Zurich. After that, an attempt is made to derive an empirical law of bed-load transport based on recent experimental data. We desire to state expressly that by bed-load transport is meant the movement of the solid material rolling or jumping along the bed of a river; transport of matter in suspension is not included.