Combined preservative, and fire-retardant systems were pressure impregnated into Douglas fir and Ponderosa pine samples and evaluated for decay, flammability, and mechanical properties. The objective was to identify cost-effective systems for use with mine timber, and to provide an information and data base from which federal code regulations could be established. Thirty systems, based on combinations of commercially available preservatives and fire-retardent impregnants and coatings, were applied to douglas fir samples and evaluated for decay and flammability. The 10 most promising systems were applied to both fir and pine and reevaluated for decay and flammability before and after water leaching. The five best systems were evaluated in the laboratory using both pine and fir including flame spread, smoke density, toxic gases, decay, compressive strength, flammability after artificial weathering, and cost. All systems had acceptable toxic gas levels and smoke densities, but flame spread was only borderline acceptable for most of the samples tested. Recommendations are made for further large- scale testing using the two best systems.