Mild cognitive impairment (MCI) is a clinical diagnosis in which deficits in cognitive function are evident but not of sufficient severity to warrant a diagnosis of dementia. For the majority of patients, MCI represents a transitional state between normal aging and mild dementia, usually Alzheimer's disease. Multiple subtypes of MCI are now recognized. In addition to presentations featuring memory impairment, symptoms in other cognitive domains (eg, executive function, language, visuospatial) have been identified. Neuropsychological testing can be extremely useful in making the MCI diagnosis and tracking the evolution of cognitive symptoms over time. A comprehensive test battery includes measures of baseline intellectual ability, attention, executive function, memory, language, visuospatial skills, and mood. Informant-bassed measures of neuropsychiatric symptoms, behaviors, and competency in instrumental activity are also included. Careful assessment can identify subtle deficits that may otherwise elude detection, particularly in individuals of superior baseline intellectual ability. As we move closer to disease-modifying therapy for Alzheimer's disease, early identification becomes critical for identifying patients who have an opportunity to benefit from treatment.