Pentachlorophenol (PCP) is a widely used wood-treating chemical that is applied to wood under pressure in the form of concentrated solution in solvents that are nonaqueous phase liquids (NAPL). As a result, any spill at a wood-treating site using PCP results in soil contamination with PCP in the presence of a NAPL. Hence, a study of migration of PCP was conducted in presence of kerosene as a NAPL in unsaturated soils. Addition of kerosene to soil caused a change in the effective size of soil particles; the porosity, pore velocity, and dispersion coefficients, all changed (as measured by bromide breakthrough) in soil columns contaminated with kerosene. Moisture content of soil was found to be a key parameter determining the residual NAPL content in the soils. PCP/kerosene breakthrough experiments showed that the organic phase penetrated deeper and faster into soils with higher moisture content, and the residual kerosene acted as a sorptive phase that retarded the migration of PCP.