Introduction: Soil hydrophobicity is the inability of a soil to get wet easily or to allow water to infiltrate dry soil (Figure 1 , Doerr et al., 2010). Understanding soil hydrophobicity is important for soil scientists and land managers because it directly affects runoff and erosion. The main cause of hydrophobic soils is combustion. Post-fire soil hydrophobicity causes decreased infiltration rates leading to observed increases in post-fire runoff and erosion (Doerr et al., 2010). This study will focus on the effects that fire-induced hydrophobicity has on infiltration and runoff. Figure 1: Water droplets resisting infiltration into a highly porous hydrophobic soil (Doerr, 2007). A better understanding of the causes of soil hydrophobicity is needed. to understand its effects on infiltration and runoff. Fire is not the only factor that can induce water repellency in soil. Soils can be slightly hydrophobic with low to moderate moisture contents under burned or unburned conditions (Doerr et al., 2010). Different combinations of vegetation and soil type can develop strong soil water repellency. Soils under certain vegetation types with oil- or wax-rich leaves (e.g. shrubs, conifers, and eucalyptus) are more susceptible to becoming hydrophobic than soils under broad-leaved vegetation (Doerr et al., 2010). Soil particle size also plays a role in the susceptibility to developing water repellency. Coarser soils are more prone to becoming water repellent than finer soils due to the smaller surface area and number of potential adsorption sites for organic molecules (DeBano, 1981). How does fire cause soil hydrophobicity? Burning induces soil water repellency by volatilizing hydrophobic organic compounds in litter and topsoil (Doerr et al., 2010). This results in the development of a pressure gradient within the leaf litter or topsoil that causes some compounds to be pushed into the atmosphere while others are forced into the soil (Doerr et al., 2010). As the gas seeps into the soil, it cools at depth causing condensation on soil particles at or below the soil surface. This phenomenon creates a waxy coating around soil grains that causes them to repel water. Laboratory studies show that soil water repellency is intensified at soil temperatures of 175-270°C, but is destroyed at temperatures above 270-400°C (Doerr et al., 2010). Once a soil becomes hydrophobic it does not always stay that way; in fact, most soils become less hydrophobic or lose their hydrophobicity over time. Both burned and unburned soils become less hydrophobic or lose their hydrophobicity completely as soil moisture increases.