First developed in the USA in the early 1970s, 'wetland mitigation banks' provide a framework for conservation activities that are designed to offset residual, unavoidable damage to the natural environment caused by development activities. The concept is now a worldwide phenomenon. In this paper I consider the level of success of wetland mitigation banks in the USA for biodiversity conservation with a view to informing 'best practice' in Australia. I conclude that although the concept has merit, even in the USA where the processes have been evolving for over 30 years, the outcomes frequently fall short of the target of a 'like for like' swap of habitat. While the outcome for wetland mitigation may not be an 'unmitigated disaster' it is, at best, apparently only modestly successful.