Determining if and when a potential accident scenario is subject to requirements of the National Environmental Policy Act (NEPA) of 1969 has long been an open question. This issue is routinely addressed by some agencies, yet is virtually ignored by others. Certainly, not all federal proposals merit a detailed analysis of accident scenarios. Yet, how does one determine under which circumstances an analysis of accident scenarios should be subject to a NEPA analysis versus those that are not? The implications of this issue are particularly important with respect to low-probability high-consequence events. Beyond the obvious risk of increased exposure to litigation, this question is of interest for other reasons, not the least of which being that such an analysis can substantially increase schedules and cost. This paper examines this question and provides a tool consisting of seven tests for assisting practitioners in reaching a determination.