The interfacial and thermodynamic properties of water/CPC/alkanoL/alkane (C-6 and C-7) and water/DDBS/1-pentanol/n-heptane w/o microemulsion systems were investigated by the method of dilution. The rationale for the equation used by earlier workers to process their data was clarified, and the criticism made in a recent paper on the relationships used in the dilution method was shown to be unjustified. The composition of the cosurfactant and the surfactant in the interfacial region, the distribution of the cosurfactant between the interfacial region and the continuous oil phase, and the energetics of transfer of the cosurfactant from the oil to the interface were estimated. A correlation between the free energy of transfer and the alkanol carbon number was examined.