Memory can be assessed with either explicit or implicit tasks. Implicit memory tasks, in contrast with explicit tasks, do not refer to conscious recollection of a previous learning experience. Implicit memory is revealed by a change in task performance that can be attributed to previous learning. Amnesic patients perform poorly on explicit memory tasks, but exhibit normal performance on implicit tasks. Recently, researchers have studied the implicit memory performance of patients with Alzheimer's disease. This article aims to give an overview of the performance of Alzheimer patients on four tasks of implicit memory. Compared with normal elderly controls, patients with Alzheimer's disease seem to demonstrate impaired performance on conceptual, but not on perceptual, implicit memory tasks. This dissociation could yield important information about the neurologic systems subserving implicit memory processes. Some suggestions for future research into the implicit memory of Alzheimer patients are given.