It is a common finding that 30–90% of people experiencing serious illness and other forms of adversity report increased quality of life and other positive life changes after their experience, yet there is still considerable disagreement among scientists and practitioners about whether such changes are real or beneficial. The current article identified four pervasive assumptions about positive emotions and beliefs that may limit progress in understanding and promoting resilience among survivors of cancer, namely, that positive beliefs and emotions are absent, dangerous, delusional, or trivial among people managing life-threatening illnesses. A review of evidence on each of these points suggested instead that positive emotions and beliefs seem not only to be associated with good outcomes among people experiencing adversity, but also to play a role in realizing them. Implications for the study of positive beliefs, emotions, and life changes among survivors of cancer and for interventions to promote mental and physical health were discussed. Cancer 2005. © 2005 American Cancer Society.