Two decades of research examining repetition priming in aging and Alzheimer's disease (AD) has yielded a large body of contradictory findings due to differences between studies in participant and task characteristics. Recent research that has employed methodological advances indicates that this form of implicit memory is preserved in healthy aging. When a priming deficit does occur in studies of aging, it is likely a very early signal of neurological disease. Future directions for research in this area include linking priming ability to known risk factors for development of AD, integrating priming measures into clinical neuropsychological assessment batteries, and implementing programs of cognitive retraining that enhance memory using stimulus repetition techniques.