A mediated amperometric enzyme electrode sensitive to NADP(+) was developed by co-immobilization of ferrodoxin-NADP(+) reductase and viologen amino derivatives of different chain length (C-3, C-6 and C-10) on the surface of a glassy carbon electrode. Glutaraldehyde cross-linking in the presence of bovine serum albumin was used for immobilization. Communication between the redox centre of the enzyme and the electrode through the immobilized mediator was proved, and a fast electrical response in the presence of NADP(+) was obtained. The best results were achieved with a medium-sized viologen. The sensitivity and linear response range depended on the polymer thickness and the immobilization procedure affected the stability of the modified electrode.