The National Clinical Guideline Centre (NCGC) develops evidence-based clinical guidelines on behalf of the National Institute for Health and Clinical Excellence (NICE) in the United Kingdom. The U.K. Department of Health has commissioned NICE to make recommendations on the basis of both clinical effectiveness and cost-effectiveness. This article describes how cost-effectiveness is evaluated and accounted for in NCGC guidelines. Six recent case studies are presented, in which consideration of cost-effectiveness has informed recommendations in various ways for clinical guidelines on alcohol use disorders, chronic obstructive pulmonary disease, glaucoma, lower urinary tract symptoms, non-ST-segment elevation myocardial infarction and unstable angina, and venous thromboembolism prophylaxis. Some of the challenges faced in trying to account for cost-effectiveness in clinical guidelines are outlined, as well as some of the difficulties in adapting cost-effectiveness guidelines for other settings.