Mixed aqueous micellar solutions of sodium dodecylsulfate+potassium dodecylsulfate and sodium dodecylsulfate+sodium ethoxydodecylsulfate have been studied. Experimental data on the critical micelle concentration (CMC) versus the relative concentration of two surfactants, results of the micellar solution/liquid crystal and liquid solution/solid phase equilibrium measurements are presented. The data obtained are interpreted in the framework of the pseudo-phase model of micellar solutions. The effect of salts added to solutions of dodecylsulfates is discussed.