Most waterfront structures are built of wood because of its low initial cost and permanence when properly treated. However, premature failures caused by decay in the above-water portions can occur even though the wood used has been pressure-treated with preservatives. Decks and large horizontal structural members (curbs, wales) are particularly prone to decay, often developing seasoning checks that expose untreated heartwood. Also, fender piles are frequently damaged by interior decay resulting from infection of untreated heartwood exposed when the pile top is cut to height. The problem is particularly severe with species such as Douglas fir containing large portions of heartwood, which are difficult to pressure-treat. This article reports the 15-year results of experiments established in 1969 to determine the potential of (a) in-place treatment of deck planking with fungicides for controlling decay in untreated wood or pressure-treated wood having checks that penetrate the zone of preservative treatment and (b) cap and fungicidal treatment for protecting from decay the cut tops of newly installed piles. Earlier articles reported details of the experimental design and observations through 10 years.