Laboratory experiments were conducted in straw fuel beds in order to characterize the effect of a widely used long-term retardant on fire behavior under different conditions: no slope-no wind, upslope-no wind, and no slope-upwind. The results are reported in terms of reduction factors for a set of variables characterizing fire behavior. In the experimental conditions the values of upslope-no-wind and no-slope-upwind fires showed no statistically significant differences from those of no-slope-no-wind fires. For all types of fire, values obtained for the reduction factors on rate of spread, fuel consumption ratio, fire intensity, and flame length were 63%, 36%, 77%, and 54%, respectively.