Cancer survivors are often highly motivated to seek information about food choices, physical activity, dietary supplement use, and complementary nutritional therapies to improve their treatment outcomes, quality of life, and survival. To address these concerns, the American Cancer Society (ACS) convened a group of experts in nutrition, physical activity, and cancer to evaluate the scientific evidence and best clinical practices related to optimal nutrition and physical activity after the diagnosis of cancer. This report summarizes their findings and is intended to present health care providers with the best possible information on which to help cancer survivors and their families make informed choices related to nutrition and physical activity. The report discusses nutrition and physical activity issues during the phases of cancer treatment and recovery, living after recovery from treatment, and living with advanced cancer; selected nutritional and physical activity issues such as body weight, food choices, and complementary and alternative nutritional options; and selected issues related to breast, colorectal, lung, prostate, head and neck, and upper gastrointestinal cancers. In addition, handouts containing commonly asked questions and answers and a resource list are provided for survivors and families. Tables that grade the scientific evidence for benefit versus harm related to nutrition and physical activity for breast, colorectal, lung, and prostate cancers are also included for this growing body of knowledge to provide guidance for informed decision making and to identify areas for future research. © American Cancer Society, 2003.