Invasive species are a growing threat in the United States, causing losses in biodiversity, changes in ecosystems, and impacts to economic enterprises such as agriculture, forestry, fisheries, power production, and international trade. The costs of preventing and controlling invasive species are not well understood or documented, but estimates indicate that the costs are quite high, in the range of millions to billions of dollars per year. EPA’s Office of Water needs to develop a national estimate of the costs of aquatic invasive species and the benefits of control. This review of the economic literature on invasive species is the first stage in the development of that estimate. The review includes studies on fish, mollusks, crustaceans, invertebrates, and plants. There are few theoretical, and even fewer empirical, studies dealing with the economic costs of aquatic invasive species. Due to the high level of invasions in the Great Lakes, a number of studies focus on species found there, and on Zebra Mussels in particular. The aquatic studies reviewed show values ranging from several hundreds of thousands of dollars a year to tens of millions of dollars a year. It seems apparent that a systematic approach is needed to develop a consistent method to estimate such costs. As the literature points out, invasive species and their control have definite public good aspects and thus call for some level of government intervention. However, to what extent and what form that intervention takes place depends on myriad of issues associated with both the region and the species involved. Optimal policy appears to be as unique as the individual species or ecosystem it is attempting to control and protect.