The effect of excitation and emission wavelengths on fluorescence decay times of Chlorophyll a were measured in four solutions (C approximately 10(-5) mol X 1(-1] and in polymethyl methacrylate films. The decay times observed were corrected with respect to self-absorption and re-emission effects. The fluorescence decay times of Chlorophyll a was found to depend on both the excitation and the emission wavelengths.