Dominant commercial treatments currently used for wood preservation are pentachlorophenols (PCPs), creosote, and chromium copper arsenicals (CCAs). These wood preservatives present many studied and documented environmental and toxicological problems both with use of the products themselves and with the production of secondary reaction contaminants. Furthermore, several of these preservatives are considered priority pollutants according to the U.S. Environmental Protection Agency (EPA) and are heavily regulated. The need for an environmentally benign combined fire/rot retardant treatment for wood that will effectively reduce both fire and decay is clearly evident. Guayule resin, a co product during rubber extraction from the guayule shrub, is being explored by us as a natural, biodegradable wood rot and fire retardant with potential commercial applications. Wood impregnated with guayule resin has survived over 8 years in a tropical rain forest environment, free of rot, decay, and insect infestations. This study qualitatively analyzed treated and untreated wood samples For ignitability, flame spread, toxic fumes, and smoke generation. Ignitability of the wood sample of fixed geometry was quantified by measuring the time required for ignition of treated samples versus untreated samples. Flame spread was measured after ignition with a propane flame by a simple stopwatch-ruler technique. Smoke mass was determined in an Arapa-hoe Smoke Chamber as per ASTM D-4100. Analysis of the fumes involved continuous CO, C02, NOx, SOx, and O2analyses using a Bacharach Instrument Model NSX 300. An Andersen Inc. Model 2000 cascade impactor was used to determine the particlesize distribution of the smoke and for smoke mass. Most of the differences in the test data measurements between guayule-impregnated pine and untreated pine were found to be minor. However, the ignition data indicated that guayule-impregnated pine did not ignite as quickly as untreated pine. Based on the favorable data presented herein, further research of wood preservation with guayule resin is recommended.