From the beginning of fire research efforts in Canada, forest fire behavior research has been empirical in nature, producing fire behavior predictions based on models derived from field experiments. The models relate fire behavior to weather based fuel moisture codes and relative fire behavior indexes. Experimental fire sizes attempt to reflect equilibrium fire behavior conditions for the chosen fuel/weather conditions. Laboratory-based research in moisture physics and heat transfer theory provide the framework by which the field data are analyzed. The Canadian Forest Fire Behavior Prediction System is the culmination of this research on quantitative fire behavior. The ongoing goal is the production of a universal fire behavior model combining field experimental evidence with physically-based models.