Experiments have been done in order to determine the effects of particle size and bulk density on the erosion of quartz particles. Average particle sizes ranged from 5 to 1,350 μm, while bulk densities ranged from approximately 1.65 to 1.95 g/cm3. For the larger particles, the sediments behaved in a noncohesive manner, i.e., they consolidated rapidly and the surface eroded particle by particle. For the smaller particles, the sediments behaved in a cohesive manner, i.e., they consolidated relatively slowly and the surface eroded in chunks. Erosion rates were a very strong decreasing function of density for the finer particles and were essentially independent of density for the larger particles. For a particular bulk density and shear stress and as the particle size increased, the erosion rate increased rapidly for the smaller particles, reached a maximum, and then decreased rapidly for the larger particles. Critical stresses for erosion were strongly dependent on particle size and, for the smaller particles, were also strongly dependent on bulk density.