Book excerpt: Whether it is to understand the networks of individuals, the physical makeup of a household or community, or to develop strategies for finding difficult-to-reach populations such as the homeless or drug-addicted, applied researchers increasingly need to understand spatial methods. In this brief volume, the techniques of network analysis, mapping, and finding hidden populations are explained in simple, practical language. The authors describe when and how to use these techniques and offer numerous examples of how the methods have worked in community psychology, drug research, risk assessment, and network analysis, among other settings.