Lagoons for industrial wastes have developed out of simple holding pits to contain solids and remove water by evaporation, infiltration, or overflow. The eventual failure of such lagoons has led to more sophisticated management of various types. Lagoons are used to provide one or more of the following treatments: mixing and equalization of loads, clarification and retention of solids, dewatering, chemical neutralization or conversion, and removal of biologically active materials. Each of these functions is discussed with emphasis on the ultimate fate of the materials that have been placed into the lagoon. (Author)