Accelerated leaching tests were made to estimate the service life of creosote treatments. A respirometer method was developed for large-scale screening of creosote fractions for toxicity of Limnoria. Preliminary results indicated that the tar acid fraction was extremely toxic. The cellulase enzyme system of Teredo was observed to be active and present in the larvae at the time of penetration of the wood. The cellulytically active material was extracted for study. Analysis of intermediates of carbohydrate metabolism indicated the presence of adenylic acid, adenosine di- and tri-phosphates, hexose phosphates, and arginine phosphate. Studies were started on the histological changes in the larvae. Tests indicated that the intensity of borer attack was independent of the duration or conditions of water soaking of the wood before exposure. Creosote protected wood only to a small degree with 18 in. of the edge treated part. Antifouling paints with CuO were effective at more than 12 in. Greenhart panels exposed for 3 yr showed light attack by Teredo and Limnoria Surinam timber panels exhibited light to heavy attack after 2 yr.