Results from the first two years of operation of the OTEC Seacoast Test Facility in Hawaii are presented. No detectable biofouling from cold water in smooth tubes has been observed. Intermittent, low-level chlorination appears to control biofouling from warm water in smooth tubes. Uniform corrosion of all aluminum alloys is low in warm water, with no pitting observed. In cold water, preliminary data indicate pitting of all alloys, but corrosion is considerably less uniform than in warm water.