Partitioning behavior of organic contaminants in the vadose zone may be influenced by the presence of a nonaqueous phase liquid (NAPL). The bulk NAPL phase not only serves as a sink for hydrophobic contaminants but may also cover a significant fraction of the soil surface, reducing the surface area available for vapor-solid adsorption. Experiments were carried out to examine the applicability of binary partitioning parameters when applied to a multiphase system. Dodecane was used as the model NAPL phase, while toluene and benzene were used as the model hydrophobic contaminants. Several soil types and water contents were examined. Results indicated that two-phase equilibrium parameters were sufficient to predict partitioning among the various phases if fractional soil surface coverage by each phase was considered. A previously developed model was extended to account for the presence of NAPL and was used to describe the multiphase contaminant partitioning presented in this work. ¿ 1998 American Geophysical Union