Invasive species are a leading threat to aquatic biodiversity and ecosystems. Because invasions are among the most irreversible of human impacts, prevention is the most important approach for dealing with this problem. But with approximately 15,000 lakes in Wisconsin, how do we focus our efforts most effectively? We have been working with a variety of researchers on what we call 'smart prevention' projects. The idea is to identify lakes that are most likely to be invaded and most likely to be impacted by an invader.