The Agency expends a significant proportion of its budget to measure levels of contaminants or effects of contamination in the environment. In addition, it mandates that other organizations, primarily private companies, expend considerable resources to provide measurement data to the Agency. This requires that decisions be made concerning appropriate sampling methods and analytical techniques and results in huge volumes of measurement data that must be evaluated and interpreted by Agency personnel. Concerns such as extent of contamination, potential health risks due to the contamination, and likelihood of adverse health consequences by introduction of new chemicals into the market place are just a few of the decision areas based on these data. Clearly the potential health consequences and economic implications of these evaluations and interpretations are very significant. Hence it is very important that the best expertise be brought to bear on these decisions. The purpose of the paper is to review the development of expert systems by US EPA to assist in evaluation of measurement data.