FireStem is a computer model designed to aid fire managers in predicting tree mortality based on fire behavior and intensity. The eventual goal is to produce mortality predictions based on fuel information, moisture, and fire behavior for a specified region and a range of tree species. FireStem is based on fundamental thermodynamics and heat transfer taking into account the thermophysical properties of individual species in order to predict temperature at the living tissue or cambium. Eventually, the user will be able to input a range of species for a given ecosystem, run FireStem, and review the mortality prediction for a range of diameters for each species. To date, we have developed and validated FireStem for four species, Douglas Fir, Ponderosa Pine, Chestnut Oak, and Red Maple. The mortality predictions used in FireStem are based on recent work by Dr. Matthew Dickinson at the USFS Northeastern Research Station and include the latest understanding of cambial tissue response to thermal injury. Other species will be added as their thermophysical properties are identified and validated.