The ethical basis of clinical outcomes measurement is a desire to improve care in a way which will increase both clinical effectiveness and value for money-beneficence as well as competence. To date in the U.K., any debate about producing comparative indicators of clinical outcomes has been concerned mainly with the unfairness to individual doctors or clinical teams of judging their performance on this basis. There has been less interest in the prime purpose of such production, which is to increase the accountability and effectiveness of the NHS as a publicly funded service. Rather than working to improve clinical effectiveness and outcomes within clinical services, health authorities which wish to improve outcomes for their populations have been encouraged simply to shift the contract to another provider of care. The key issue on which the ethics of either action rests is the extent to which the attribution of outcome to intervention is valid and reliable and, therefore, that judgements about performance are just and thus ethical. The consequence of unjust judgements may be to increase the inequalities that medical care resource allocation should attempt to reduce.