Purpose: This study examined the association between cognitive functioning and completion of a durable power of attorney for health care. Design and Methods: Participants were from the Second Longitudinal Study on Aging (LSOA II), a nationally representative sample of community-dwelling persons who were at least 70 years of age at the time of participation. The sample included 325 older adult respondents (144 men, 181 women) with a mean age of 80.7 years (SE = 0.36) and a mean educational attainment of 11.6 years (SE = 0.18). Researchers measured each respondent's cognitive functioning during follow-up by using an adapted Telephone Interview of Cognitive Status, and a proxy informant indicated whether the respondent completed a durable power of attorney for health care. Results: A durable power of attorney for health care was completed by 60.8% (SE = 2.51) of respondents prior to their death. Logistic regression demonstrated that respondents with the first quartile of global cognitive functioning were 76% less likely to have completed a durable power of attorney (adjusted odds ratio = 0.24, 95% confidence interval = 0.09-0.60) than those with the fourth quartile of cognitive functioning. Implications: The factors associated with completion of durable power of attorney for health care by older adults with lower levels of cognitive functioning should be investigated further. Such data could be used to inform interventions to increase the completion rates of durable power of attorney for health care among this particular group of older adults. (Contains 1 figure and 4 tables.)