This chapter describes how casemix measures are being used by Doncaster Health Authority to help ensure that it achieves the greatest possible health gain from the resources available for the 300000 people for whom it has responsibility. Doncaster Health Authority should thereby achieve value for money by paying a price which is more closely related to the cost of providing the treatment. Comparative data are being used in order to benchmark provider performance to identify areas where there might be scope for efficiency gains or improved outcomes and to assess the appropriateness of levels of activity purchased. The role of health authorities and Primary Care Groups/Trusts as purchasers of health care includes ensuring that services provided represent value for money. In an ideal world this would be assessed by comparing the costs of treatment between different providers. The National Health Service (NHS) Executive measures health authorities' performances in meeting efficiency gain targets using the 'efficiency index'.