The oscillatory fluorescence of the Ru-ion-catalyzed Belousov-Zhabstinsky reaction has been studied and analyzed in relation to the fluorimetric behavior of the isolated Ru(bpy)(3)(2+) ion. Here we show how different forms of fluorescence oscillations, observed at various excitation wavelengths and Ru(bpy)(3)(2+) concentrations are due to an inner filter effect of the isolated Ru(bpy)(3)(2+) ion. Three types of phase relationships, i.e., in-phase, opposite-phase; and complex phase relationships, between oscillatory fluorescence and the oscillatory Ru(bpy)(3)(2+) concentration can be predicted and have experimentally been observed.