Informal payments in the health sector in Eastern Europe and Central Asia (ECA) is emerging as a fundamental aspect of health care financing and as a major impediment to health care reform. Private payments to public doctors, nurses, and other health personnel are essentially an informal market for health care occurring within the confines of public health care service networks. These expenditures are also outside the financial controls, policy rubric, and audits of countries' health care systems. Like the informal sector, it is often illegal and unreported, and despite the terminology, is a form of corruption. 'Who is Paying for Health Care in Eastern Europe and Central Asia?' outlines the key policy issues, summarizes available data on the scope and nature of informal payments across ECA and spells out the policy implications and possible strategies to address the problem.