Technical Abstract: Broom snakeweed (Gutierrezia sarothrae) is a very aggressive native invasive species which can thrive after disturbance in semi-arid areas of the western U.S. The objectives of this study were to evaluate the ability of four plant community phases within the same sagebrush shrub-steppe community to resist snakeweed invasion over a 5-year period (2002-2006), and to develop a state-and-transition model for range managers to use as a tool to minimize snakeweed invasion. The study site originally had two plant community phases: phase 1 received alternate-year, fall cattle grazing, and was dominated by bluebunch wheatgrass (Elymus spicatus) and an open stand of Wyoming big sagebrush (Artemisia tridentate ssp. wyomingensis); phase 3 received continuous, annual spring cattle grazing and was dominated a dense stand of Wyoming big sagebrush with an understory of Sandberg bluegrass (Poa secunda). Portions of phases 1 and 3 were burned in a 2001 wildfire, removing the Wyoming big sagebrush, and creating phases 2 and 4. Phase 2 was dominated by bluebunch wheatgrass, and phase 4 was dominated by Sandberg bluegrass. Four 10 m transects were placed within each phase. Densities of shrubs and snakeweed were counted in 1 m x 10 m belt transects and foliar cover was estimated by the line intercept method. Over the 5 year period, snakeweed cover in phase 1 was reduced from 3.1% to 0%, due to suppression from the bunchgrasses and sagebrush; snakeweed in phase 2 was removed by the fire, and there was no reinvasion; snakeweed cover in phase 3 remained unchanged at 4.1%; snakeweed cover in phase 4 steadily increased from 2.3% to 31%. Snakeweed age class densities in phase 4 showed the progression of snakeweed invasion. The stand progressed from 26.6 seedlings/m2to 12.0 mature plants/m2. The above ground biomass production showed that Phase 4 had the highest snakeweed biomass (833 kg/ha) and phases 1 and 2 had the highest total above ground biomass (2430 kg/ha). The results suggest that bluebunch wheatgrass or big sagebrush will resist snakeweed invasion and expansion on a sagebrush-steppe site. A state and transition model was created for managing snakeweed in this sagebrush-steppe com