Steady-state and time-resolved fluorometry, quasielastic light scattering, and viscometry were used to study solution behavior of fluorescently tagged poly(methyl methacrylate) (PMMA) in binary mixtures of 1,4-dioxane with either 2,2,3,3-tetrafluoropropanol (TFP) or methanol. In 1,4-dioxane/TFP mixtures, which are good solvents for PMMA, an intermolecular association occurs. It was shown by time-resolved fluorometric measurements that the unusual behavior of PMMA in good solvent mixtures is due to association of nonpolar fluorophores in a polar medium. Association processes were not detected in systems containing a virtually identical, but nontagged PMMA sample in the same solvent mixtures. In mixed solvents of 1,4-dioxane/methanol, association of the tagged (as well as nontagged) sample does not take place.