The present study was designed to determine whether neuropsychological deficits exist in asymptomatic first-degree relatives of Alzheimer's disease (AD) patients. The neuropsychological performances of 20 first-degree asymptomatic relatives of NINCDS-ADRDA diagnosed AD patients were compared to 20 normal controls without family history of AD. Cognitive functions assessed included intelligence, memory, overall brain function, verbal learning, and language and constructional abilities. Significant statistical differences were found between the groups across several cognitive areas indicating lower functioning in the first-degree relatives of AD patients. Fifty percent of the first-degree subjects but only 20% of controls showed a pattern of significant neuropsychological deficit. The results demonstrate neuropsychological deficits in asymptomatic first-degree relatives of AD patients, suggesting that preclinical markers for AD may be present long before the clinical manifestation of the disease.