Unlike other areas of guideline development, there is little practical or theoretical experience to direct the incorporation of cost issues within clinical guidelines. However, the reasons for considering costs are clearly stated by Eddy: 'Health interventions are not free, people are not infinitely rich, and the budgets of (healthcare) programmes are limited. For every dollar's worth of healthcare that is consumed, a dollar will be paid. While these payments can be laundered, disguised or hidden, they will not go away'.1 Such opportunity costs are not particular to the healthcare system of the USA, but a universal phenomenon; the NHS needs to obtain the best value from finite public funds.