The increased use of wetland creation or restoration as compensation for losses permitted under Section 404 of the Clean Water Act has focused attention on the efficacy of this practice. The U.S. Environmental Protection Agency's Wetlands Research Program is studying wetland creation. Research is underway to synthesize knowledge on wetland creation and restoration; describe trends and patterns in Section 404 permitting; and compare created and naturally occurring wetlands. The comparisons of created and natural wetlands were designed to develop standard methods that could be used to quantitatively describe wetlands nationwide with known accuracy, precision, and comparability. An extensive sampling approach, i.e., sampling of populations of wetlands, was chosen to increase the limited general knowledge on created wetlands. Created and natural sites were characterized through measurements of biological, physical, and chemical parameters. Results from these studies will be used to generate hypotheses to be tested using an intensive sampling approach, i.e., experiments performed at a limited number of sites.