A novel photosynthetic bioelectrochemical cell that utilizes biocatalysts in both anode and cathode compartments was constructed for the first time, in the anodic half-cell, some parts of the electrons produced by the oxidation of water in the photosystem of cyanobacteria are transferred to the carbon felt anode through quinonoid electron transfer mediators. The electron is passed to dioxygen to regenerate water in the cathodic half-cell reaction with an aid of bilirubin oxidase reaction via a mediator. The maximum electric power was about 0.3-0.4 W m(-2) for the projective electrode surface area at an apparent efficiency of the light energy conversion of 2-2.5%. The factors governing the cell output are discussed on the basis of the potential-current curves of each half-cell.