Ascorbate oxidase [EC 1.10.3.3] was purified from cucumber, Cucumis sativus, and its molecular weight and other physicochemical properties were investigated. This enzyme contains 8 atoms of copper per molecular weight of 132,000 and has a specific activity of 3,500 Dawson's units/mg. Results on spectrophotometric and ESR measurements, as well as those on kinetic analysis and azide inhibition of the enzyme, are also presented.