Herbaceous layer vegetation responses to prescribed fire and fire surrogate treatments (thinning and understory removal) were examined. Results from 3 to 4 years following treatment are presented for the Ohio Hills Country and the Southern Appalachian Mountain sites of the National Fire and Fire Surrogate Study. At the Ohio Hills site, changes in forest structure were observed for all treatments, but areas treated with fire showed the greatest increase in herbaceous cover and species richness. These results indicate that fire effects are unique disturbances that are not mimicked by alterations of the forest structure alone. However, at the Southern Appalachian site, fire alone did not produce a response in the herbaceous layer. The combination of fire plus mechanical treatment was necessary to increase cover and species richness.