The electroreduction of 3-phenyl azo-2,4(3H,5H)-furandione and five of its phenyl-substituted derivatives in aqueous ethanolic buffered solutions (pH approximate to 2-12) have been investigated at the DME. The acid dissociation constants were determined spectrophotometrically. A mechanism for the electroreduction pathway is proposed. On the basis of the data obtained the azomethine linkage is thought to be in the azo and not the hydrazone form.