The simultaneous ion exchange extraction of selected pairs of noble and base metal cyano complexes was studied. In most cases It was found that equilibrium Is attained only after a period of several hours during which time the resin composition undergoes marked variations. As a rule, the loading of noble metals passes through a maximum value while the loading of base metals Increases steadily as equilibrium Is approached. Kinetic parameters, obtained by applying mathematical models to the experimental data, indicated that there are significant differences in dlffusivity among the various metal cyano complexes in both the Nernst diffusion layer and in the resin matrix. These differences assist in understanding the experimental observations.