The effect of sodium bromide concentration on the simultaneous adsorption of dodecylpyridinium bromide and sodium octysulfonate on the free surface of their aqueous solutions has been investigated. The composition of the mixed films adsorbed from equimolar solutions has been evaluated on the basis of the Gibbs adsorption equation and by using the regular solution model. It has been stated that this composition depends on the surface tension value and the concentration of added inorganic electrolyte. The same factors influence the value of the surface interaction parameter beta; negative values indicate a strong attraction between the adsorbed components. The concentration ratio of both surfactants in the solution significantly influences the composition of anionic-cationic adsorption films and the mutual interactions of their components. A distinct difference in the effects of NaBr and NaCl on the properties of the mixed monolayers has been also found.