We regard this book as a truly joint effort arising from our common concern to improve the quality of economic evaluation in the health care field. For a number of years we have been independently engaged in teaching, research, and consultancy in this area. In particular we have offered advice to colleagues from other disciplines and on many occasions have been part of multidisciplinary teams undertaking evaluations of programmes or treatments. These experiences have convinced us of the need for a book which discusses the methodological principles of economic evaluation in health care in a way that would benefit those who plan to undertake such studies.