According to the recent worldwide estimation by the GLOBOCAN project, in total, 12.7 million new cancer cases and 7.6 million cancer deaths occurred in 2008. The worldwide number of cancer survivors within 5 years of diagnosis has been estimated at be almost 28.8 million. Informal caregivers, such as family members and close friends, provide essential support to cancer patients. The authors of this report provide an overview of issues in the study of informal caregivers for cancer patients and long-term survivors in the United States and Europe, characterizing the caregivers commonly studied; the resources currently available to them; and their unmet needs, their psychosocial outcomes, and the psychosocial interventions tailored to their special circumstances. A broad overview of the state of research and knowledge, both in Europe and the United States, and observations on the directions for future research are provided. Cancer 2013;119(11 suppl):2160-9. © 2013 American Cancer Society.