Subjects from four Mexican families at risk of inheriting Alzheimer's disease (AD) were studied using a complete neuropsychological battery. These tests were repeated and compared 1 year later. Some of the experimental subjects belong to an international protocol on molecular chromosomal study. A control group matched in age and schooling was included. The subjects at risk underwent a complete physical, neurological and neuropsychological assessment. A neuropsychological battery of cognitive domains designed for the the study of dementia syndromes was administered to all subjects. Six of the subjects showed abnormal performance in cognitive functions, memory, visuospatial functions or language which persisted 1 year later. The present work describes the initial findings of a long-term prospective study aimed at delineating the neuropsychological profile of subjects at risk and to validate subtle abnormalities which in some cases could be the incipient changes of AD.