Electric power utilities are familiar with and skilled in preparing for and responding to almost-routine natural hazard events such as strong wind and ice storms and seasonal floods, as well as intentional human acts such as vandalism. Recent extreme weather (hurricanes Katrina and Rita), extremely destructive international earthquakes (in Sumatra and Pakistan), and nation-wide concerns regarding future terrorist attacks have increased the pressure on utilities to take appropriate steps to avoid being overwhelmed by such infrequent and exceedingly severe events. Determining what constitutes the appropriate steps to take requires various levels of understanding of the specific hazards and the risks faced by the utility. The American Lifelines Alliance (www. americanlifelinesalliance.org) has prepared a Guideline that provides clear, concise, and nationally-applicable guidance on determining the scope and level of effort necessary to assess power system performance in the wide range of natural hazard or human threat events. Included in this Guideline are specific procedures to follow and information to consider in performing standardized assessments. With the results of such assessments, utility owners can effectively establish and carry out risk management programs that will lead to achieving appropriate levels of performance in future events. The Guideline incorporates an inquiry-driven process with a two-phase performance assessment that can be applied to power systems of any size. The screening phase enables systems or components that are clearly not at risk to be screened out early. The subsequent analysis phase uses results from the screening phase to prioritize and allocate resources for more detailed assessments of hazard, vulnerability, and system performance. This process helps assure that the scope of the assessment meets the specific performance objectives of the inquiry. A case history is presented to illustrate the type of experience with an inquiry-driven process that was considered in developing the Guideline to meet the diverse needs of utility personnel in engineering, operations, and management. Copyright ASCE 2007.