A laboratory study was made of the characteristics of streams flowing over a loose bed of fine sand in order to determine what factors govern the equilibrium rate of transportation of fine sand in suspension. Twenty-two experimental runs were performed in a 40-ft tilting flume for various conditions with bed sand of two different sizes (0.10 mm and 0.16 mm). Each run represented a uniform open-channel flow in equilibrium with the sand bed. Because of the extreme variability of channel roughness, the transportation rate could not be expressed as a unique function of the bed shear stress, the channel geometry, and the properties of the sand. This is contrary to all previous theories for the equilibrium transportation rate of suspended load. At low velocities, the large irregular dunes which formed on the stream bed made the bed friction factor more than six times larger than the friction factor for the smooth sand beds obtained at higher flow rates. By using the mean velocity and the depth (or the water discharge and sediment discharge) as independent variables and the slope as a dependent variable, an orderly qualitative relationship between the pertinent variables was obtained.