Comparative maps have been a valuable resource for extrapolating biological information among organisms. The relationship between mouse and human maps provides a framework for integrating information from each species and thereby increasing the utility of all available data such as gene location, structure and function. This review describes the various public resources, both databases and web sites, containing genome-wide mouse-human comparative map information available through the World-Wide Web. We will focus on the use and applicability of these resources in their current form and consider future potential directions.