The Delis-Kaplan Executive Function System (D-KEFS; Delis, Kaplan, & Kramer, 2001a) is a set of standardized tests for comprehensively assessing higher-level cognitive functions, referred to as "executive functions," in both children and adults (aged 8 to 89). Executive functions draw on the individual's more fundamental or primary cognitive skills (i.e., attention, language, and perception) to generate higher levels of creative and abstract thought. The D-KEFS is made up of nine tests that measure a wide range of verbal and nonverbal executive functions. Each test is designed to be a stand-alone instrument that can be administered individually or along with other D-KEFS tests, depending on the assessment needs of the specific examinee and/or the time constraints on the examiner. This review presents a description of the components, standardization, applications, reliability, and validity of the D-KEFS. The author concludes that the D-KEFS is an innovative and promising tool in the measurement of executive functioning in both clinical and nonclinical populations. In clinical populations, the D-KEFS can be used to assess mild brain damage in general and mild frontal-lobe involvement in particular. In school settings, it can be used to complement the assessment of those abilities measured by traditional tests of intelligence and achievement tests with the assessment of higher-level cognitive abilities. This is particularly important in the assessment of learning disabilities, the assessment of attention deficit/hyperactivity disorder (ADHD), and the assessment of gifted students.