The phase behavior and solubilization of multiphase microemulsions in mixed anionic-cationic surfactant systems were studied for fixed ratios of waler 10 diesel oil and surfactant to alcohol. In the mixed surfactants (sodium oleate + cctyltrimcthylammonium bromide) ldicscl oill a1cohol/watcr systems, microcmulsion and birefringent phases are formed by adjusting the surfactant ratio E and the cationic weight fraction O. The bicontinuous-ebircfringcnt-e-o/w microcmulsion transition takcs place with dilution for i-pentanol-containing systems, The birefringent region shrinks rapidly with increasing alcohol and/or CTAB weight fractions in total surfactant concentration. The normal solunon-sw/o microemulsion transition for n-hexanol systems and only wlo microemulsion for n-octanol systems were observed along the dilution with diesel oil and water. And microemulsiou domain enlarges with increasing E for three alcohol systems. The optimum surfactant concentration y increases and the corresponding optimum /) decreases with increasing E and the optimum y decreases with increasing the alcohol chain length from i-pentanol to n-octanol and the optimum () decreases in the order of i-pentanol > n-octanol > n-hexanol. Conductivity