Amyloid beta-peptide (A beta) plays a critical role in the development of Alzheimer's disease (AD). Much progress has been made in understanding this age-related neurodegenerative disorder; thus an insight into the cellular actions of A beta and resulting functional consequences may contribute to preventive and therapeutic approaches for AD. In this review, recent evidence of A beta-induced brain dysfunction, especially cholinergic impairment and memory deficits, is summarized. Moreover, proposed mechanisms for A beta-induced neurotoxicity such as oxidative stress, ion-channel formation, and A beta-receptor interaction are discussed.