The use of fire behavior models is an essential element in the development of proactive fire management systems. Silvicultural activities and the associated changes in stand structure in turn affect in-stand microclimate processes and fuel complex characteristics that influence fire behavior. The complexity of the processes that determine fire behavior makes it necessary to use models that integrate the various variables controlling fire behavior that in turn produce quantitative descriptions of potential fire behavior, namely probability of ignition, fire spread and intensity, and the likelihood of crown fire development. The use of models allows one to address questions like: 'What levels do surface fuel loads need to be maintained at in order to reduce the likelihood of crown fire initiation?', 'For a given silvicultural system, what is the target canopy cover in avoid the possibility of active crown fires?', and 'Under what conditions is a stand considered largely a barrier to surface fire propagation but yet could allow for the development of active crown fires?'. The complexity involved in assessing the fire environment coupled with the inherent limitations of fire behavior simulation systems can lead to erroneous results that might induce mismanagement with long-term, unwanted consequences. In the present work we describe several case studies of the application of crown fire behavior models to evaluate the effects of silvicultural treatments on fire potential and discuss the main limitations of this approach. We also argue for the need to monitor microclimate processes (e.g., wind and fuel moisture) and determine their effect on fire potential. Note: Is the English translation of the title of a paper (Cruz, Alexander and Viegas 2005) presented at the 5th National Forestry Congress sponsored by the Portugese Society of Forestry Sciences (http://www.spcf.pt) held in Viseu, Portugal, May 16-19, 2005.