U.S. Government regulations require that all effluents from industrial operations, including mining, meet certain water quality standards. Constructed wetlands have proved useful in helping to attain those standards. Application of this biotechnology to mine water drainage can reduce water treatment costs and improve water quality in streams and rivers adversely affected by acidic mine water drainage from abandoned mines. Over 400 constructed wetland water treatment systems have been built on mined lands, largely as a result of research by the U.S. Bureau of Mines. Wetlands are passive biological treatment systems that are relatively inexpensive to construct and require minimal maintenance. Chemical treatment costs are reduced sufficiently to repay the cost of construction in less than a year. The mine waste water is typically treated in a series of excavated ponds that resemble small marsh areas. The ponds are engineered to facilitate bacterial oxidation of iron. Ideally, the water then flows through a composted organic substrate supporting a population of sulfate-reducing bacteria which raises the ph. Constructed wetlands in the United States are described-- their history, functions, construction methodologies, applicabilities, limitations, and costs.