Risk quantification can help in understanding and managing risk. Establishing quantitative risk criteria can be a key component to risk decision-making and many companies use such criteria, either formally or informally. The Center for Chemical Process Safety issued its guidance on developing quantitative safety risk criteria in 2009-Center for Chemical Process Safety Guidelines for Developing Quantitative Safety Risk Tolerance Criteria. This article addresses some of the more common challenges that users may face in developing and implementing safety risk tolerance criteria as they apply the Guidelines. (C) 2011 American Institute of Chemical Engineers Process Saf Prog 30: 232-239, 2011