We develop a framework for valuing improvements in health and apply it to past and prospective reductions in mortality in the United States. We calculate social values of (i) increased longevity over the twentieth century, (ii) progress against various diseases after 1970, and (iii) potential future progress against major diseases. Cumulative gains in life expectancy after 1900 were worth over $1.2 million to the representative American in 2000, whereas post‐1970 gains added about $3.2 trillion per year to national wealth, equal to about half of GDP. Potential gains from future health improvements are also large; for example, a 1 percent reduction in cancer mortality would be worth $500 billion.