Site characterization and biofouling studies were conducted at a site about seven miles north of St. Croix, U.S. Virgin Islands, during July to September, 1977. The devices basically consisted of aluminum pipes (8' long x 1'' ID) through which seawater flowed at rates of 3 or 6 ft sec/sup -1/. The units were mounted on the deck of a barge, moored in water of depth about 4000 m, and seawater for the experiment was obtained from a depth of about 20 m ATP and carbon and nitrogen contents, microbial plate counts (bacteria, yeasts, filamentous fungi) were employed as measures of biofouling films within the aluminum pipes. Chlorophyll a and phaeo-pigment determinations indicated that viable and dead photosynthetic microbes were insignificant in the fouling films. No major differences in biofouling were observed between the two seawater flow rates, either in the CMU or RSMAS pipes. The general conclusion from the site characterization work is that the nutrient and microbial loads in the surface waters at the St. Croix site are low. The site is therefore suitable for OTEC, beacuse biofouling should be minimal, although this conclusion is qualified by the need for seasonal and longer-term evaluation.