The diagnosis and treatment of cancer can be an extremely stressful, and possibly traumatic, experience. Not surprisingly, there is considerable research documenting the potential negative psychosocial sequelae of malignant disease. More recently, however, research has documented that a broad range of both positive and negative psychosocial outcomes might follow cancer diagnosis and treatment. This suggests that a sole focus on distress and dysfunction could paint an incomplete and potentially misleading picture of the cancer experience. Evidence suggesting that cancer could be a traumatic stressor for some patients is reviewed, as is evidence suggesting that it might precipitate both posttraumatic stress and posttraumatic growth, at times within the same individual. We conclude by offering a conceptual model of cancer as a psychosocial transition. Rather than viewing cancer as a trauma with uniformly negative effects on quality of life, it might be more appropriate to view cancer as a psychosocial transition with the potential for both positive and negative outcomes.