This chapter deals with the interactions between organic chemicals and soil fractions—i.e., soil material making up the subsoil. Although some of the mechanisms and processes involved will be like those attributed to interactions between soil fractions and inorganic contaminants, others will be different due to the specific properties of organic chemical contaminants. Unlike heavy metal contaminants, organic chemical contaminants will degrade and can volatilize. We will be primarily concerned with the abiotic reactions between the organic chemicals and soil materials in this chapter. We recognize that biological reactions are major contributors to the processes which serve to attenuate organic chemical contaminants. Chemical mass transfer is responsible for partitioning of contaminants in the fate and transport of contaminants. Reduction-oxidation reactions can also play important roles in the fate of the contaminants. Assessment of whether the processes lead to retention or retardation is necessary if one wishes to determine the mobility of the contaminants. If potential contaminant hazards and threats to public health and the environment are to be minimized or avoided, we must ensure that the processes for contaminant attenuation are irreversible or below the levels of allowable limits or levels. We need to know how partitioning of the organic chemical compounds occurs and also the degree to which an organic chemical contaminant is available for biologically mediated transformations.