The close of the twentieth century brought historic changes in cancer risk factors, early detection, and treatment. As a consequence, we have seen two decades of steadily declining risk of death from cancer in the United States. The reasons for declining cancer mortality rates are largely known: reduced tobacco use, the adoption of cancer early-detection methods, and better cancer therapeutics. Despite this progress, disparities in cancer mortality persist across different groups defined by race and social class. Because all the factors that account for declining cancer trends are influenced strongly by social class, and because of large social class disparities in cancer risk factors, there will likely be a widening gap in cancer mortality among those in lower socioeconomic groups in the future. This article reviews the trends in risk factors for cancer mortality and discusses the persistent problem of disparities by race and social class.