Over the last decade, there has been an increased interest in using survey techniques to measure the cognitive functioning of older, noninstitutionalized persons. Simultaneously, there has been rapid growth in understanding the cognitive processes used by respondents of all ages to answer survey questions and how these processes affect the quality of survey responses. In this chapter, we discuss why the quality of the responses of older respondents may differ cognitively from those of younger ones. We present some data from a sample of older adults to illustrate how cognitive processes affect survey measures of cognitive functioning and how cognitive interviews may be used to understand these effects.