This paper describes an inventory of wetlands constructed for acid water treatment. Preliminary results, based on the 20 sites surveyed to date, indicate that the wetlands dominated by emergent species are out-performing the sphagnum-dominated wetlands. In general, iron concentrations as high as 85 mg/l are reduced to less than 3 mg/l after flow through the constructed wetlands. Manganese is also removed, though somewhat less efficiently. The ph at the discharge, if not above 6, can be raised to that level or higher by flow over limestone. Wetland performance appears to increase in the second year after construction as vegetation becomes better established, and if inflow water volume is regulated, constructed wetlands can provide effective treatment of acid mine water at a relatively low cost.