In summary, we have reviewed the recent literature on the use of GIS in exposure assessment for environmental epidemiology and described principles and applications of three core scientific disciplines needed, in our opinion, to successfully implement such studies: geospatial science, environmental science, and epidemiology. This by no means preempts the need for other scientific disciplines in the execution of such studies. In particular, statistics is a core science that would benefit every study, and other disciplines should be included based on the focus and objective of the study. Based on our findings, we offer the following conclusions: