Different mononuclear and dinuclear Cu complexes show high catalytic activity at concentrations 1-10 muM in the oxidation of ascorbic acid by peroxynitrite. Their activity is similar to the activity of Mn-porphyrin complexes and weakly depends on ligand environment, provided at least one free coordination site is available. The proposed reaction mechanism involves the intermediate formation of a copper-peroxynitrito complex, which reacts directly with ascorbic acid.