Experiments were carried out to compare the shift of absorption bands for a number of solutions of pure dyes with the corresponding fiber/dye system. It was found that in the fiber/dye system, dye degradation occurs according to first-order kinetics. The amount of degradation depends on the wool/nylon blend ratio, the dye structure, the functional groups in the fiber/dye system, the diffusion coefficent of the dye and the number of amino end groups in the fiber. -- AATA