Eicosapentaenoic acid ethyl ester (EPA-Et) was successfully transported against its concentration gradient from a n-dodecane solution to a m-xylene solution through a bulk liquid membrane as well as a supported liquid membrane containing silver nitrate as a carrier. The principle of this uphill transport is that the distribution ratio of EPA-Et, which is defined as the ratio of the equilibrium concentration of EPA-Et in an aqueous silver nitrate solution to that in an organic solution, is highly dependent on the solvent of the organic phase. n-Dodecane gives a much higher distribution ratio than m-xylene. This is the first demonstration of uphill transport by use of solvent dependence of the distribution ratio of a permeant solute.