Neuropsychological assessment has been utilized extensively in the research of cognitive outcomes associated with medical illnesses, such as HIV, and post-surgical procedures, such as coronary artery bypass graft. However, few investigations of intensive care unit (ICU) survivors have examined cognitive function as a clinical outcome. Significant clinical questions exist regarding the impact of critical illness on long-term cognitive function. Many of these questions can be systematically evaluated through the use of standardized neuropsychological assessment instruments within the context of well designed, prospective research trials. This review will provide information for clinical researchers interested in the study of neuropsychological outcomes in intensive care unit survivors ( a comparison article in this issue will address clinical issues related to cognitive functioning).