To group or not to group, that is the question addressed by a panel of independent experts in a recent study. Recognizing that different PFAS have widely different physical, chemical and toxicological properties, the experts provided responses to a series of questions and feedback on each others’ responses, all without knowing who the other experts were. The published study compiles the independent results and describes where consensus did and did not occur. The majority of panelists agreed that grouping, as suggested by US EPA, is a pragmatic place to start in assessing effects, but not sufficient for health-based regulation. The panel split on when dose additivity would be justified beyond a screening step, and no consensus was reached on the utility of total organic fluorine measurement as a screening tool.