This booklet is intended for those who use (or who would like to use) the evidence produced from economic evaluation to inform decision making in health, and for those who conduct economic evaluations intended to inform decision making in health. It explains the Gates-Reference Case (GatesRC), why it is important, and how to use it. This booklet is a summarized version of the full Gates-RC, which can be found in the Methods for Economic Evaluation Project Final Report, published by NICE International (www.nice.org.uk/niceinternational).