We have developed an electrochemical antibiofouling system for plate heat exchangers that employs heat exchange plates as the electrodes. A field experiment was performed using plates made of titanium or Pt/IrO2-coated titanium. Iron bar and silver-silver chloride electrode were set inside of the heat exchanger, and used as a counter and reference electrode, respectively. The reactive current reached equilibrium above seawater flow at 1.0 m(3) h(-1), and a uniform potential distribution was observed. Electrochemical antibiofouling experiments were performed using seawater as the secondary cooling water, which was pumped through a strainer into the plate heat exchanger at a flow rate of 1.66 m(3) h(-1). Organism's attachment on the heat exchange plates was prevented for over 1.5 years by the electrochemical treatment.