The recently published CCAC guidelines: Categories of welfare impact is part of a series of general guidelines documents on the ethics and care of all animals used in scientific activities. This specific document acknowledges that the welfare of animals used in science can be impacted in diverse ways, and describes how expected welfare impacts to animals should be determined and summarized into a descriptive category, and then confirmed retrospectively. This session offers the opportunity to discuss the new guidelines and share best practices and challenges for the transition from categories of invasiveness to categories of welfare impact.