Fire frequencies averaged 32 to 70 years in sagebrush-grass communities. Early spring and late fall fires are the least harmful to perennial grasses, although small plants and those with coarse stems are more tolerant of fire than large plants and those with leafy stems. Cheatgrass can be suppressed by burning in early summer, but the set-back is only temporary and perennials such as Idaho fescue and Stipa sp. are easily killed during this season of the year. Most forbs can easily tolerate fall burns, but not much data are available for early spring burns. The three sub-species of big sagebrush are easily suppressed by fire. They may or may not become re-established quickly after fire, depending on seed source. Antelope bitterbrush is very susceptible to fire, but some genotypes resprout if moisture is adequate following a burn. Rabbitbrush and horsebrush resprout vigorously after fire. All known data on the effects of fire on plants are summarized in this report. Drought, competition, and fire played a complementary role in limiting the distribution of pinyon and juniper before grazing by domestic livestock became an influence. Natural fires occurred every 10 to 30 years, which kept the junipers restricted to shallow, rocky soils and rough topography. Heavy livestock grazing has reduced fuel for fires and has permitted pinyon and juniper to rapidly invade adjacent communities. Pinyon and juniper trees less than 1.2 m tall can easily be killed where there is adequate fine fuel to carry a fire, but dense stands of pinyon and juniper with bare soil may require an initial, expensive renovation procedure involving mechanical treatment, prescribed burning, and seeding. Thereafter, however, young pinyon and juniper trees can be kept out of the grassland or sagebrush-grass with a maintenance fire every 20 to 30 years. Mixtures of sagebrush and pinyon-juniper can be easily burned without fine fuel on the ground. Only alligator juniper is a sprouting species. Effects of fire on grasses, forbs, and shrubs are covered in detail. Guidelines for conducting prescribed burns in sagebrush-grass and pinyon-juniper communities are presented. The guidelines should be used with the understanding that further research is needed to refine all prescriptions.