Some Oregon ports use untreated Douglas-fir decking and timbers above the waterline in marine structures. This can lead to early decay and increased maintenance. Several methods for controlling such deterioration are evaluated. Simulated piers were constructed of untreated Douglas-fir caps, stringers, and decking, and protected by various combinations of methods. Protection methods included: 1) application of pentachlorophenol, copper-8-quinolinolate, fluor-chrome-arsenic-phenol (FCAP), ammonium bifluoride (ABF), or boron; 2) use of treated roofing felts between members; and 3) kerfing to control checking. The structures were supported by pressure-treated piles of Douglas-fir. The members in the piers were examined over six years for checking and decay. Kerfing reduced the incidence of decay in all members. ABF, alone or in combination with a felt, and FCAP-flooded felt produced the best results. However, any of the chemicals tested would improve performance of Douglas-fir in piers. These results suggest that the tested treatments, if applied when a structure is built, can delay decay and prolong service. -- AATA