The interaction of aluminum(III) with phosphatidylcholine (PC) small unilamellar vesicles (SUV) was investigated by H-1 NMR utilizing EuCl3 as a shift reagent, An upheld shift of outward facing choline methyl signal of PC SUV was induced by addition of Eu3+ to a PC SUV suspension, This was markedly reduced by subsequent addition of AlCl3 and InCl3 to the suspension. Addition of several other divalent metal chlorides (MgCl2, CaCl2, NiCl2, and ZnCl2) did not reduce the Eu3+-induced shift. The line broadening of choline methyl signal brought about by addition of Fe2+ or Fe3+ to PC SUV suspensions was further enhanced by subsequent addition of AlCl3. From these results, we conclude that Al3+ and In3+ interact with the phosphate group of PC molecules on the outer surface of SUV and displaces the bound Eu3+. The interaction of Fe2+ and Fe3+ with PC SUV appears to be enhanced by Al3+, Our results also indicate that In3+ binds stronger to PC SUV than Al3+,