A review. The fuel/water partitioning coeffs. of a large range of polar aliph. and arom. fuel components are described. The data presented suggest that polar fuel components behave distinctly differently from known fuel constituents, such as BTEX, in a point source release scenario. As shown for aniline, the low values of the fuel/water partitioning coeffs. of polar fuel constituents imply that fuels in contact with groundwater will be efficiently extd. This leads to a rapid depletion of such compds. in a nonaq.-phase liq., causing a transient compn. of the contaminant plume with elevated aq. concns. of polar compds. at the leading edge of the plume.