Because of advances in early detection and treatment, cancer has become a curable disease for some and a chronic illness for others. Underscoring this change, persons with diagnoses of cancer increasingly are described as "cancer survivors" rather than "cancer victims". Cancer survivors include all living persons who ever received a diagnosis of cancer. To highlight how the population of cancer survivors has changed in the United States, the National Cancer Institute and CDC studied cancer data collected during 1971-2001. This report summarizes the results of that study, which determined that the number of persons living with cancer increased from 3.0 million (1.5% of the U.S. population) in 1971 to 9.8 million (3.5%) in 2001. A national health objective for 2010 is to increase to 70% the proportion of cancer patients who are living > or =5 years after diagnosis, an objective already achieved for children with cancer but not yet for adults. The growing number of persons living with cancer poses challenges for researchers to understand the physical, psychosocial, and economic effects of surviving cancer and for public health practitioners to develop evidence-based programs to promote the health and well-being of cancer survivors.