Herein, we report the results of a study of surface and micellar properties of alkanediyl-alpha,omega-bis(dimethyl-cetylammonium bromide) gemini surfactants in pure aqueous solutions and also in the presence of alcohols (butanol, hexanol) and amines (butylamine, hexylamine). Parameters studied include cmc (critical micelle concentration), C(20) (concentration required to reduce the surface tension of the solvent by 20 mN center dot m(-1)), Gamma(max), (maximum surface excess concentration at the air/solution interface), and A(min) (minimum area per surfactant molecule). These parameters indicate mixed micellization between the surfactants and alcohols/amines; therefore, surfactant-additive interactions in mixed micelles and mixed monolayers, as well as activity coefficients, are also calculated. All the results show that high additive concentrations destabilize micelles: Delta G(ex), (excess free energy of micellization) becomes more negative at low additive concentrations (i.e., micelles stabilize) and less negative at high concentrations (i.e., micelles destabilize).