We introduce a new source of detailed data on spending by medical condition to analyze US health care spending growth in the period 2000-14. We found that thirty conditions, which represented only 11.5 percent of all conditions studied, accounted for 42 percent of the real growth rate in per capita spending during this period, even though they accounted for only 13 percent of overall spending in 2000. Primary drivers of spending growth included the use of new technologies, a shift toward the provision of preventive-type services, and an aging and more obese population. The health benefits of many new technologies appeared to outweigh the associated expenditures on treatment, which indicates that these are cost-effective and provide a net value to society. However, while these technologies may be of value, new treatments are often more expensive than older ones.