In addition to dissolved and dispersed hydrocarbons, produced water usually contains some solids. The solids are predominantly of reservoir origin and are usually coated with a thin film of oil. This paper discusses the origin and need for separation of such solids from produced water. The paper includes an identification of the adverse effects of the solids, which include erosion and environmental considerations. In the case of produced water reinjection, solids removal for the prevention of reservoir plugging is discussed. Basic process theory of solid-liquid hydrocyclones is presented. The paper also discusses the performance characteristics in produced water application. Finally, results from a recent successful offshore pilot plant trial using a high pressure desanding hydrocyclone are presented.