Abstract: A microemulsion composition for treating the hair, comprising a water-insoluble amino-containing compound, such as an amine or an amino-functionalized silicone; an ionizable metal salt, wherein the metal has a valence of at least II, such as magnesium chloride or zinc chloride; an ester compound having the general structural formulaR.sub.1 --O--(A).sub.X --CH.sub.2 CO.sub.2 R.sub.2,wherein R.sub.1 is an alkyl group including from about eight to about 18 carbon atoms, R.sub.2 is an alkyl group including from one to about four carbon atoms, A is an alkylene oxide moiety wherein the alkylene group includes from one to about four carbon atoms, and X is a number in the range of from about 4 to about 20; and water, and wherein the composition has a pH of less than 7 and a particle size in the range of from about 0.1 nm to about 250 nm, to impart durable conditioning properties to treated hair is disclosed.