This article reviews ozonation of the public water supply at Monroe, Michigan. In place since 1979, the ozonation system has effectively destroyed tastes and odors under all conditions. The following beneficial side effects of ozonation at the Monroe plant are discussed: improved performance of alum in ozonated water; higher quality water to the filters; extended filter runs with less head loss; reduced frequency of backwashing; effective destabilization of colloidal waters; reductions in chlorine demand; reduction in concentration of trihalomethanes and trihalomethane formation potential; partial disinfection; destruction of cyanide; and improved water quality monitoring. The author describes reliability of the equipment, ozone generation and availability of materials for operation and maintenance of the ozone plant, automatic and manual control of the system, safety of the system, and economics of the system. Includes 7 references, table.