The results of contact angle measurements on polystyrene (PS) or poly(styrene/methacrylate) (PSMA) surfaces with aqueous dioctadecyldimethylammonium bromide (DODAB), chloride (DODAC), or acetate (DODAc) dispersions in the range 10(-6)-10(-4) M are reported. At each concentration two separate angles were measured : initial advancing (A) and initial receding (R). For the polystyrene surface without charge, A and R decreased as a function of amphiphile concentration (C) for all surfactants. For the charged copolymers, A and R first increased and then attained a plateau value as a function of C. In the presence of DODAB, DODAC, and DODAc dispersions, constant contact angles attained on the PSMA surface with the highest charge density were 85, 72, and 67 degrees, respectively. In this case, hysteresis, which is generally very large for soluble surfactants, was absent. Counterions effect on the nature of the deposited surfactant layer is to increase hydrophilicity according to acetate > chloride > bromide. For pure polystyrene, amphiphile molecules lie on the hydrophobic homopolymer. In contrast, increasing the surface charge on the polymer surface promotes a high degree of vertical orientation of the hydrocarbon chains.