The pre-Columbian mixed-growth form, composition, and structure of sagebrush steppes was mostly due to the highly variable semiarid climate and long fire-free intervals. The weak stability of this relatively complex vegetation was easily upset by excessive livestock grazing, especially in drought periods. After a few decades of uncontrolled livestock grazing, it was easy for introduced winter annuals, especially cheatgrass, to dominate the understory and alter the fire regime to larger, more frequent fires that occur earlier in the year. Accelerated soil erosion has caused many sites to lose the potential for management back toward native perennial dominance by controlling only livestock and fire. Major investments will probably be necessary to lengthen the current fire-free interval, as well as reduce the size of fires and their occurrence during late spring and early summer on large areas of cheatgrass dominance. Livestock could be used in some circumstances to help reverse the damage they did before grazing became regulated. Opportunities to apply genetic engineering to native plants and new herbicides to cheatgrass should also be explored before even more noxious biennials gain a major foothold.