6575 Background: There is ample evidence that the death rate in elderly patients increases in winter months. The increase in deaths may be amplified in terminally ill patients where place of care home, hospital, or long-term care facility might play a significant role in seasonal mortality. In this paper, we compare seasonal variation in death rates for terminally ill cancer patients to terminally ill patients who are “frail,” i.e., those with neurodegenerative disease, general debility, or chronic heart failure. Methods: We reviewed monthly deaths for Medicare patients age 65 or older with terminal cancer or “frail” patients who were admitted to one of 45 hospice programs and died on service between January 2004 and November 2008. The 72,066 records were analyzed using a three-way analysis of variance (season, place of care, diagnosis) with Bonferroni correction for post-hoc comparisons. Results: Compared to frail patients who died during June, July, and August, the number of deaths of frail patients increased an average of 20% in January, February, and March. This near-sinusoidal pattern was remarkably consistent over a five year period. The effect was most pronounced in patients in nursing facilities, followed by those in hospital, and then by patients receiving home care (all p < 0.005). For cancer patients, this seasonal variation was not observed in any place of care (all p > 0.05). Conclusions: Although frail patients generally have a longer length of stay in hospice than cancer patients hence allowing more opportunity for exposure to infection a number of other factors may serve to insulate cancer patients from seasonal effects. These include a smaller “symptom burden” than frail patients, who frequently have comorbid disease(s) and who are often unable to make their needs known; less compromised immune systems; more aggressive medical treatment; better nutrition; a strong support system (particularly from family and caregivers); and increased sensitivity to factors that may prolong survival, e.g., timely immunizations and even the avoidance of crowds in winter months. No significant financial relationships to disclose.