The phase diagram of the sodium docecyl sulfate (SDS)/1,2-octanediol/water system at 25.0 +/- 0.1 degreesC is given in this paper. The system shows an isotropic normal micellar phase at high water concentration, and two liquid crystalline phases characterized as the hexagonal phase and the lamellar phase. The diol behaves as a short-chain alkanol, except that the extended lamellar phase is stabilized at a very low SDS content. The lamellar phase is also formed by 1,2-octanediol with water. The rheology technique was applied to characterize the phases. The lamellar phase can be divided into four different zones according to the flow behavior. Some of the samples close to the boundary show structural transitions induced by shearing. Both liquid crystalline phases are very elastic, but they show very different relaxation times. The surfactant concentration affects size, stiffness, and the dynamic properties of the cylindrical units in the hexagonal phase.