How is medicine doing at the end of the twentieth century? While there has been no end of studies of our health care system and proposals for changing it, there have been few credible studies of the risks and benefits of widely used medical treatments. We simply do not always know whether one treatment is better than another or whether a particular drug is worth the price.

Medical technology assessment is the discipline that studies what does and does not work in medicine. Howard Frazier and Frederick Mosteller are leading figures in this field. In Medicine Worth Paying For...