Low density lipoproteins are highly sensitive to oxidation by copper salts, and such peroxidation is accompanied by macrophage scavenger receptor recognition. This study shows that fresh human atherosclerotic material (aneurysms and endarterectomies) can contain detectable amounts of redox active iron and copper that is chelatable from tissue homogenates. Such material is often prooxidant towards lipid peroxidation and deoxyribose degradation. Aneurysms and endarterectomies contain ferroxidase 1 activities, whereas only in aneurysms could caeruloplasmin be immunologically detected. Ferroxidase 2 activity, characteristic of a copper-oxidised lipoprotein complex, could not, however, be detected in any of the atherosclerotic samples. A third ferroxidase activity, attributable to xanthine oxidase, was present in several aneurysms and endarterectomies.