The American Petroleum Institute and the California MTBE Research Partnership have produced a new software utility to help site managers, water purveyors and regulators evaluate the sensitivity of a groundwater resource to a potential release of compounds of concern (e.g., an MTBE oxygenated fuel). The toolkit examines three aspects of sensitivity: Resource Value, Receptor Vulnerability and Natural Sensitivity. The user supplies site-specific information and the toolkit returna a "scorecard" addressing the three aspects of sensitivity. Although this utility was designed with petroleum hydrocarbon releases in mind, it can be used when dissolved chlorinated and inorganic compounds are the chemicals of concern. The toolkit runs on Microsoft Excel and comes with a user's guide.