Historical evidence indicates that fires were prevalent in grasslands. In the past, big prairie fires usually occurred during drought years that followed l to 3 years of above-average precipitation, which provided abundant and continuous fuel. Fire frequency probably varied from 5 to l0 years in level-to-rolling topography and from l5 to 30 years in the rougher, dissected topography containing rough breaks and rivers. This paper contains basic ecological information, vegetative descriptions, and fire effects data for the shortgrass, mixed grass, and tallqrass prairies in the southern, central, and northern Great Plains. In the appendix, fire effects data have been tabulated for each species for quick reference. Prescription guides are provided for all major vegetation types where prescribed burning data have been collected. In the shortgrass prairie, grasses do not benefit from prescribed burning, but fire can be used to clean up uprooted brush, kill small juniper, and kill cactus. Prescribed fire has a wider variety of uses in the mixed and tallgrass prairies, particularly if the burns are conducted following winters with above-average precipitation. Major benefits of prescribed burning are to control undesirable shrubs and trees, burn dead debris, increase herbage yields, increase utilization of coarse grasses, increase availability of forage, improve wildlife habitat, and to control exotic, cool-season grasses. Often, several objectives can be achieved simultaneously. Prescribed fire frequency should not be more often than 5 to 8 years in a 20-inch (5l-cm) precipitation zone but can be as often as 1 to 3 years in a 35- to 40-inch (89- to l02-cm) precipitation zone. Good soil moisture in the upper l ft (0.3 m) of soil is especially important before conducting a prescribed burn if the goal is to increase yield and palatability of forage. If control of shrubs is the primary consideration, such as in juniper country, burning during drought years may have the best long-term effect. To use prescribed fire is not as dangerous as most people think, providing it is done by experienced personnel. We recommend a minimum of 2 years of prescribed burning experience under a range of weather conditions for individuals having major supervisory responsibilities. Moreover, we recommend that supervisors be trained in planning and conducting burns and in evaluating the weather. To achieve a desired effect and for safety, one must have the skill to recognize, and the patience to wait for favorable weather.