Cancer related fatigue (CRF), defined by the National Comprehensive Cancer Network as a distressing, persistent, subjective sense of physical, emotional, and cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity, can severely interfere with activities of daily living, physical capacity, and ability to work. There are even reports of fatigue being a factor in patient requests for hastened death. CRF can represent a serious clinical problem after all treatment has ended. In our research with cancer survivors 1 to 3 years after completion of hematopoietic stem cell transplant (HSCT), 40% of those we interviewed reported that CRF was a major obstacle to the resumption of usual activities. Despite its impact on quality of life, CRF is under-reported, under-diagnosed, and under- treated. There is no widely accepted CRF intervention that has demonstrated clinical efficacy. A variety of pharmacologic agents have been studied to treat CRF; most notably psychostimulants, antidepressants, and corticosteroids. But there is not sufficient evidence to recommend the use of any of the currently available pharmacologic agents. A number of non-pharmacologic strategies have been tested. The most promising are exercise and cognitive-behavior therapy (CBT). Results from two randomized clinical trials suggest that exercise and CBT are equal in overall efficacy, but with only moderate effects. Indeed, at this time there is no gold standard treatment for CRF. One promising new intervention for CRF is bright white light (BWL --- systematic daily 30-minute exposure to bright white light from a commercially available lightbox) treatment. In a small randomized controlled clinical trial, BWL was protective against increases in sleep disturbances, mood symptoms and fatigue across cycles of chemotherapy. We want to investigate BWL to control CRF in 1 to 3 year survivors of HSCT for three reasons. First, CRF is a major problem for a large proportion of survivors (40%). Second, BWL may be more acceptable to survivors than CBT or exercise because BWL is less physically demanding and can be carried out at home. Third, BWL is likely to be less expensive since it can be implemented by phone, requiring less professional and patient time and effort than that required for exercise and CBT. The feasibility of the proposed research is assured by the fact that we have identified a group of 150 HSCT survivors who report clinically significant levels of CRF and who have provided informed consent to participate in further research. Specific Aims: 1) Develop and pilot test a BWL exposure intervention with HSCT survivors suffering from CRF to assess the impact on fatigue, sleep quality, and quality of life using objective and subjective measures; 2) To investigate the possible mediating effects of depression on fatigue; and 3) Assess the feasibility and acceptability of BWL as an intervention for CRF in cancer survivors.