In recent years, increased emphasis has been placed in the field of geriatric medicine on the need for multidimensional assessment of elderly patients. There is an increasing tendency to use standardized structured assessment instruments or questionnaires in this process. Frequently, the exact question or set of questions to be answered by the instrument has not been carefully analyzed. Although comprehensive structured multidimensional instruments allow the collection of large amounts of data in multiple domains (physical, social, psychologic, economic), these instruments may require excess data collection and may not be reliable in clinical settings. Clinicians considering using a variety of assessment instruments should carefully consider their goals for data collection and carefully review the validity, reliability, and population sampled for any assessment instruments under consideration. Also, the clinical setting in which the instrument is to be used can have a negative impact on either instrument validity or reliability.