This presentation is an introductory discussion about GIS aimed at those in public health interested in collaborating with GIS experts rather than using it themselves. It introduces key dimensions or topics that can be measured using GIS, typical ways to measure variables, the different geographies that are used (e.g. buffers, distances to a feature), and data sources. The focus of the presentation is on what can go wrong, that is the potential for misunderstanding between public health and built environment researchers.