There has been a spectacular explosion of therapeutic progress over the past 35 years. The consequent improvements in public health may seem self-evident. Why, then, is it necessary to employ the disciplines of economics and sociology to try to quantify these benefits? This introduction sets out to answer this question. It also looks at some of the earlier ways in which benefits have been quantified, and it discusses the reasons why new and more sophisticated methods of measurement are needed in the 1980s. Finally, it examines some aspects of the challenge presented by the new attempts to measure the social benefits of medicines. In covering this general philosophical ground, the introduction provides a backcloth against which the more detailed and practical discussions in later papers should fall into place.