Background: Metal-associated -amyloid (A) aggregates are implicated in the pathogenesis of Alzheimer disease. Results: Copper bound A(1-42) aggregates, including fibrils, degrade hydrogen peroxide, forming hydroxyl radicals and carbonyls. Conclusion: Copper-bound A fibrils can retain redox activity. Significance: A fibrils bound to copper are not inert end points and may be a source of oxidative stress in the Alzheimer brain.