The adsorption behavior of a fluorescent dye, rhodamine 6G (R6G), onto three anionic polystyrene latex samples of different charge densities has been investigated as a function of the pH and the ionic strength of the aqueous medium, The data fit well to a simple Langmuir binding isotherm, but not to a cooperative binding model. The results show that at low dye concentration adsorption depends mostly on electrostatic interactions, whereas at high concentration hydrophobic interactions prevail.