Alzheimer's disease (AD) is the leading cause of dementia for aging people, and far from control due to its obscure mechanism. Humanin, a 24-aa peptide encoded by a newly identified gene cloned from an apparently normal region of AD brain, can specifically attenuate AD-related neurotoxicity. It protects neurons from insults of various AD genes, anti-APP antibodies and Abeta by forming a homodimer outside and interfering directly or indirectly with the activity of Abeta. Humanin seems, however, not to inhibit other toxic insults to neurons, such as Fas or etoposide, an agent against carcinomatous cells in clinical therapy. So Humanin rescues neurons from various AD-related toxicity specifically with efficiency.