Interest in the influence of environmental factors on infectious disease dynamics dates back many millennia, but only recently have ecological patterns and principles been applied to pathogenic microbe transmission and prevention. “Ecological Epidemiology” has been developing over the past few decades, but from diverse disciplinary backgrounds, methods and conceptual frameworks. For this reason, there is no unified definition of “Eco-epidemiology” as a field. Similar approaches to understanding ecological patterns and processes as they relate to microbe transmission have not always used this term. At the same time, “Eco-epidemiology” has been applied to many different types of diseases, research questions, methods, and analyses. This presentation will summarize the major themes that have appeared under the heading of eco-epidemiology, and explore similarities and differences in conceptual and practical approaches being used by researchers today. How is ecological epidemiology different than any of the other sub-disciplines of ecology or epidemiology? Does eco-epidemiology have a conceptual framework that is more than the sum of those of ecology or epidemiology? Have any fundamental theories emerged that set apart eco-epidemiology from other domains or approaches? Hopefully, this discussion will help efforts to outline whether and how a unified, cross-disciplinary domain of eco-epidemiology research might be created. In addition, we can outline the contributions that ecologists can make and what challenges must be addressed.