The amyloid beta protein (ABP) is a 40 to 42 amino acid peptide which accumulates in Alzheimer's disease plaques. It has been demonstrated that this peptide and a fragment derived from it are cytotoxic for cultured cortical nerve cells. It is shown here that ABP and an internal fragment encompassing residues 25 to 35 (beta 25-35) are cytotoxic to a clone of PC12 cells at concentrations above 1 x 10(-9)M and to several other cell lines at higher concentrations. Between 10(-9) and 10(-11) M beta 25-35 protects PC12 cells from glutamate toxicity. The antioxidant and free radical scavenger vitamin E inhibits ABP induced cell death. These results have implications regarding the prevention and treatment of Alzheimer's disease.