The dynamic behavior of a dye in polymer was revealed by absorption, emission, and polarization spectra. The dye exists in monomeric form only below 0.03M concentration. At higher concentrations up to 0.6M, dimeric species exist in equilibrium with monomer, an equilibrium association constant being determined. Further increase in dye level leads to formation of larger aggregates. Fluorescence quantum yields of the monomer, dimer, and amorphous solid were found, as were their polarization ratios. The value of0.5 for the monomer indicates parallel absorption and emission transition moments with no molecular motion in the polymer within the lifetime of the singlet excited state. -- AATA