. The researchers' preliminary research has established the feasibility of this proposal. Moreover, in the preliminary research, 75% of participants completed the preliminary trial and data from the light box compliance meters showed that participants used the light boxes 80% of the days that treatment was scheduled. A large sample of fatigued MM and DLBCL ASCT survivors has been identified. The study will specifically address recommendations made for interventions for CRF from the NCI Clinical Trials Planning meeting (JNCI, 2013). It will: 1) be the first large multisite study with a carefully delineated comparison condition to investigate the effects of light on CRF among cancer survivors treated with ASCT; 2) focus on a distinct, homogenous patient population (MM and DLBCL ASCT survivors); 3) include only survivors who experience clinical levels of CRF; and 4) address possible mechanisms. This RCT will have major public health relevance as it will determine if an easy-to-deliver, inexpensive, and low patient burden intervention reduces CRF.