Stokes' law is the fundamental equation describing the settling behaviour of a particle, However, this equation is only applicable when the particle is spherical and impermeable. Therefore, it is not suitable to describe the sett-ling behaviour of aggregates found in many industrial applications due to the nonsphericity and the existence of pores in the aggregates. Many people have tried to improve Stokes' law, and have developed new models to describe the sedimentation of aggregates. In this paper, these models are reviewed. Strengths and weaknesses of these models are discussed. and potential for further development outlined.