Cats are becoming ever more popular as pets in the United States with more than 70 million pet cats noted on a recent survey of pet owners. Our understanding of feline pain has lagged behind this boom. This lecture reviews the physiology of pain, common feline pain behaviors, types of pain scales, and pain assessment tools for both laypeople and veterinary professionals with an emphasis on the Feline Grimace Scale (FGS). Learning objectives/core concepts: • Identify common pain behaviors in cats • Review pain scoring systems for cats including the CSU-FAPS, UNESP-Botucatu, CMPS-Feline, and Feline Grimace Score • Discuss the FGS in detail, including design and best practices for use • Introduce pain scoring using the FGS with real-time, group pain scoring practice