Rate of fire spread and flame length were observed on six prescribed headfires in the sagebrush (Artemisia)/bunchgrass vegetation type in western North America. Spread rate and flame length predictions from the fire behavior prediction system BEHAVE reasonably matched mean observed values from individual fires, although individual observations within a fire did not match as closely. Fuel bed discontinuity and irregular windspeed may explain most of the variation. The BEHAVE system was used to range the fuel and environmental parameters within values observed on site. This reduced the percentage of fire behavior observations outside the predicted range. Methods are discussed for sampling live and dead fuel loads and moisture contents and the behavior of fire in this vegetation type.