Waiting lists for elective surgery have been endemic to the UK National Health Service since its inception in 1948. The lists arise as a result of interaction between supply factors (the provision of resources and the efficiency of their use) and demand factors (arising from a complex conjunction of the perceptions and preferences of patients and physicians). This article takes the first steps towards the development of a macro model of the NHS waiting list. It adopts an economics perspective and assumes that the waiting time for surgery, as perceived by patients, physicians and managers, is a central influence on the quantity of elective surgery demanded and supplied. Using the methods of system dynamics, econometric results are integrated into a dynamic model that seeks to illustrate the path taken over time by the national system of elective surgery. It explores a number of future scenarios, and finds that the NHS will quickly cease to be a universal service if resources fail to keep pace with increases in demand.