It is widely accepted proposition that one of the aims of the UK National Health Service is to allocate health care on the basis of need. However, while there may be considerable consensus over the legitimacy of this goal, there is also considerable debate as to whether the goal has been met. If care is allocated according to need, then the corollary is, after controlling for difference in need, there should be no systematic differences in the amount of care received by persons of different ability to pay. Allocation according to need means that ability to pay should be unimportant. Thus an empirical test of whether the NHS allocates according to need is to examine horizontal equity in the delivery of health care, controlling for differences in need.