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The long term effects elk (Cervus elaphus), pronghorn (Antilocapra americana), and mule deer (Odocoileus hemionus) browsing on shrubs in big sagebrush (Artemisia tridentata) at high and low elevation sites in Yellowstone National Park were monitored over a 31-year period. Ungulate densities approximately doubled during the study period on the low-elevation stratum, whereas they approximately tripled on the high-elevation stratum during the same period. Therefore, ungulates were restricting Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) heights, size, and recruitment on the lower-elevation stratum only. Parallel increases in mountain big sagebrush (spp. vaseyana) densities and cover occurred over the study period on both browsed and unbrowsed sites at the higher-elevation stratum, although big sagebrush, green rabbitbrush (Chrysothamnus viscidiflorus), and horsebrush (Tetradymia canescens) were slightly taller and crown sizes were slightly larger on unbrowsed than browsed sites. Big sagebrush utilization rates were consistently high (87%) and did not differ between 1963-1969 and 1985-1988 at the low-elevation stratum study sites dominated by the more palatable Wyoming big sagebrush. Pronghorn and elk reductions during 1962-1967 apparently did not result in any percent leader use of Wyoming big sagebrush on the low stratum. Annual aboveground biomass of big sagebrush did not differ between browsed and unbrowsed study sites on the high-elevation stratum of the winter range. Population turnover was higher on browsed big sagebrush at the high-elevation plots; seedling germination and survival rates were higher on browsed plots versus unbrowsed plots. The authors suggest that the present overbrowsing of sagebrush plants is caused by uncontrolled large ungulate populations, especially at low elevations, and that reductions of ungulate populations using control programs or by reintroducing native predators (wolves) into the system are possible solutions.