In some situations, risk can be best understood, and therefore managed, through risk quantification. Establishing quantitative risk criteria can be a key component in informed risk decision making. Currently many companies use quantitative risk criteria, either formally or informally. Some companies base their criteria on regulatory precedents (e.g., Netherlands, UK HSE, etc.), while others have developed "home grown'' criteria, involving company-specific judgments. This article will provide an overview of the new American Institute of Chemical Engineers, CCPS Guidelines for Developing Quantitative Safety Risk Criteria, which is intended to provide assistance to companies seeking to develop such criteria and highlight challenges to be addressed by any company attempting to establish risk criteria. (C) 2010 American Institute of Chemical Engineers Process Saf Prog 29: 293-298, 2010