Constructed wetlands have been developed and used for treatment of municipal wastewater and have been reported widely as being low in construction and operating costs. The capital and operation and maintenance costs of both free water surface and subsurface flow wetlands are presented in this paper. Key components of construction costs are earthwork, influent and effluent structures, distribution piping, liners, planting, and roads. Construction costs for 27 free water surface constructed wetlands are summarized. Construction costs averaged about $18,200/ha ($45,000/acre) for systems treating less than 3,785 m3/d (1 mgd). Operating costs range from 0.026 to $0.08/m3 treated (0.10 to $0.30/1,000 gal treated).