Soil physical properties are those characteristics, processes, or reactions of a soil that are caused by physical forces that can be described by, or expressed in, physical terms or equations (Soil Science Society of America 2001). These physical properties (including processes) influence the mineral component of the soil and how it interacts with the other two components (chemical and biological). Plants depend on the physical characteristics of soils to provide the medium for growth and reproduction. Fire can produce significant changes in the soil that profoundly affect the ecology of plants (Whelan 1995). The effect of fire on individual soil physical properties depends on the inherent stability of the soil property affected and the temperatures to which a soil is heated during a fire. The physical mechanisms responsible for heat transfer into soils are also discussed in this chapter along with the temperatures that develop during different severities of burning in several wildland ecosystems. The relationships between soil physical properties affected by fire and erosional processes are also reviewed.